The Tome of Mighty Wondering is a legendary artifact, sought and then found and then lost and then sought and then found and etc. again and again over the years. Scholars believe the constant searching is due primarily to the grand-sounding name, as tales of spell casters actually using the spells contained in the tome are few and far between. It is supposed that often the 'losing' of the Tome is less than unintentional.

Anyone finding the Tome has access to the spells contained therein, according to the limits of their class, level, other known spells, and common sense. 

(Thanks and apologies to the classic 'Outrages from the Mages' Dragon Magazine articles :)

Age Hand (cantrip, transmutation)

Casting Time: 1A
Range: Self
Components: S, M (a bit of lizard skin)
Duration: Permanent
Casting this spell causes one of your hands (caster's choice) to immediately age 1d10 years, developing cracks, wrinkles, and sagging skin. Normal effects of aging will apply to any future tasks performed by this hand.

Charm Self (1st level, enchantment)

Casting Time: 1A
Range: Self
Components: S, M (a mirror)
Duration: 1 hour
When you cast this spell, you must make a Wisdom saving throw against your spell DC. You do so with advantage if you are currently harming yourself. On a failed save, you become intensely charmed by yourself--you are confident that your decisions are correct, and that you are 'quite the catch'. The spell ends if you intentionally do anything to harm yourself. Once the spell is over, you are aware that you charmed yourself. 

Detect Normal Missiles (cantrip, divination)

Casting Time: 1R
Range: Self
Components: S
Duration: Instantaneous
You may cast this spell immediately after taking any damage. Upon casting, you know whether you have been hit by any non-magical missiles, what those missiles where, exactly where they hit you, and how much damage each one caused. You are then free to share this knowledge with anyone in the general area.

Earth Breathing (3rd level, transmutation)

Casting Time: 1A
Range: 30 feet
Components: S, M (a worm, which is consumed by the caster)
Duration: 24 hours
This spell alters up to ten willing creatures you can see and are within range so that they are able to breathe dirt and rock as if it were air until for the duration of the spell. Note that this spell does not provide any ability to move through such materials. Also note that, when the duration is complete, those affected suffer 10d10 points of necrotic damage from the piles of dirt and rocks in their lungs.

Fire Breathing (3rd level, transmutation)

Casting Time: 1A
Range: 30 feet
Components: S, M (a small amount of whiskey)
Duration: 24 hours
This spell grants up to ten willing creatures you can see and are within range the ability to breathe fire as if it were air until for the duration of the spell. Note that this spell does not allow those affected to project this fire to cause significant damage (at the DM's discretion, someone affected by this spell might be able to cause 1d4 of damage with an attack to anyone who was close enough to blow on). While this spell prevents those affected from being harmed by the fire they are breathing, it does not provide protection from fire to any other parts of their bodies.

Lactate Animals or Plants (3rd level evocation)

Casting Time: 1A
Range: 5 miles
Components: V (caster must make baby sounds)
Duration: 1 month
Describe or name a specific kind of beast or plant. Concentrating on the voice of nature in your surroundings, you cause the nearest living creature or plant of that kind to begin producing milk (of whatever kind its species would produce--cow milk, almond milk, etc.), if any are present.

Move Earth (9th level, transmutation)

Casting Time: 1A
Range: Infinite
Components: V, S (caster must make a mime's 'wall pushing' pantomime)
Duration: Permanent
Casting this spell causes the entire planet, and indeed all of the contents of the caster's current plane of existence, to simultaneously move 5 feet to the right or left (caster's choice). The caster and any possessions, being part of that plane of existence, move along with everything else. All air and similar substances also move. Affected creatures are left with a 'funny feeling' in their stomach that lasts for 1 round.

Otiluke-Freezing Sphere (6th level, evocation)

Casting Time: 1A
Range: Current plane of existence
Components: V, S, M (a piece of ice)
Duration: 10 minutes
This spell creates a glowing, steaming sphere of terrible coldness which immediately leaves the caster's hand and seeks out Otiluke, provided he is on the same plane as the caster, and freezes him on the spot. He does not receive a save. Otiluke is unable to move or take any actions for the duration of the spell. When the spell has expired, Otiluke immediately becomes aware of the identity and location of the caster.

Pass Gas Without Trace (cantrip, abjuration)

Casting Time: 1R
Range: Self
Components: V (caster whistles softly)
Duration: 1 round
For the duration of this spell, all gas passed by the caster remains undetectable to those in the area. After the spell is over, those attempting to detect 'who dealt it' roll with disadvantage.

Protection from Food and Drink (2nd level, abjuration)

Casting Time: 1R
Range: Self
Components: V, S (caster mimes zipping mouth closed)
Duration: 1 week
This spell protects the caster from all damage taken from normal food and drink. For the duration, the caster is considered immune to all types of damage inflicted by anything the caster would normally consider edible or drinkable. Note that poisoned, spoiled, rotting, or otherwise harmful food are clearly not food the caster would normally consider edible. The caster's body can in no way be affected by these items--this includes protecting the caster from digesting these items and absorbing nutrients from them. 

Protection from Normal Kittens (2nd level, abjuration)

Casting Time: 1A
Range: 10 feet
Components: S, M (a small bag or box)
Duration: 1 minute
For the duration of the spell, anyone within 10 feet of the caster has resistance to all damage--including psychic--from all normal house cats under the age of 6 months. You are also immune to all charm effects from said kittens. Once you have cast this spell, the kittens are aware you have cast it, and they take it personally. 

Protection from Protection (4th level, abjuration)

Casting Time: 1A
Range: Touch
Components: S, V
Duration: 1 minute
This spell causes 1 willing target to be immune to the effects of any Protection spells. These include any 'Protection from X' spells, as well as all spells that prevent attacks or damage.

Purify Evil (4th level, transmutation)

Casting Time: 1A
Range: 30 feet
Components: S, M (hair from a goatee, worn or carried)
Duration: 1 hour
Casting this spell causes one or more mildly or non-committally evil creatures or objects (up to 5, caster's choice) to become 'a bit more evil'. The target creatures get a Wis saving throw to ignore the effects. This spell does not cause them to take action, and does not make them more vulnerable to attacks or spells targeting evil things (they are already evil, after all). It just makes them feel more 'totally evil' and more sure of their evilness for the duration. 

Remove Curse (1st level, abjuration)

Casting Time: 1A
Range: 30 feet
Components: V, M (a bit of soap)
Duration: 1 hour
Casting this spell causes the target, on a failed Con saving throw, to be unable to utter foul language for the duration of the spell. Any 4-letter words (or their equivalent) the target tries to speak are replaced with a steady beeping tone that is emitted from their mouth. Except for the most unusual of spells, this does not affect the target's spell casting. 

Shocking Gasp (cantrip, evocation)

Casting Time: 1BA
Range: Self
Components: V 
Duration: Instantaneous
The caster is able to emit a rather loud (but not magically loud) gasp which conveys an attitude of shock and surprise to any who hear it. 

Speak with Pants (2nd level, transmutation)

Casting Time: 1A
Range: Self
Components: V, M (a piece of denim or leather)
Duration: 10 minutes
You imbue normal and magical pants within 30' of you with limited sentience, giving them the ability to communicate with you. You can question the pants about events that have occurred around them in the past day, including anything that pants would normally be interested in--who has been wearing them, what they have been sitting on, what has been in their pockets.
You can also make difficult or ill-fitting pants easier to wear, or well-fitting pants to be more ill-fitting, causing them to relax or tighten themselves around a new wearer (within the same size class). The spell doesn't enable the pants to move by themselves or to be able to cause damage or measurable hindrance to the wearer.

Spell Check (cantrip, transmutation)

Casting Time: 1R
Range: Self
Components: V, S (caster wiggles either the ring finger or pinkie of his right hand)
Duration: Instantaneous
You may cast this spell as a reaction immediately after realizing that you have mispronounced part of a spell you just cast, or have misspelled part of a spell you are writing into a spellbook or scroll. The spell corrects the misspoken or miswritten word, allowing the original spell to work as intended. This spell does not effect a casting that fails due to loss of concentration, taking damage, etc. 

Summon Courage (cantrip, evocation)

Casting Time: 1BA
Range: Self
Components: V, S (caster holds up one finger and nods)
Duration: Instantaneous
Casting this spell causes your choice of a large tankard of ale or a shot of strong spirits to materialize in your hand. The tankard or shot glass disappears when the liquid has been emptied.

Summon the Earl (2nd level, transmutation)

Casting Time: 1A
Range: Self
Components: V, S (caster sticks finger down throat)
Duration: 1 round
Casting this spell causes you to immediately begin vomiting. You can move as normal for the duration, but you can take no actions or cast no spells for the duration.

Tasha's Hideous Daughter (1st level, evocation)

Casting Time: 1A
Range: 10 feet
Components: V, S, M 
Duration: 1 minute
Casting this spell summons Candace, the hideous and uncontrollable toddler daughter of the great wizard Tasha. Candace proceeds to run around the area surrounding the caster, screaming at the top of her lungs about wanting her 'binky' and knowing you aren't her mommy and throwing whatever she can get her hands on. All spell casters must save vs your spell DC at disadvantage in order to cast spells for the duration. All barbarians immediately begin to rage. Anyone attempting to hide is immediately found and pointed out to all others by Candace, and anyone failing an attack role or save is mocked incessantly. Being the daughter of a great wizard, Candace is magically protected from and immune to all damage and spells short of a wish. She is unable to attack or inflict damage herself. She disappears at the end of the duration, first making one final rude gesture with her fingers towards a randomly selected creature.

Transport Via Pants (6th level, conjuration)

Casting Time: 1A
Range: 10 feet
Components: V, S (caster says "I can see myself in those pants" in caster's language)
Duration: 5 rounds
This spell creates a magical link between any pair of pants within the spell's range and another pair of pants, at any distance, on the same plane of existence. You must have seen or touched the destination pants at least once before. For the duration, anyone may put on the pants and be magically transported to the location of the destination pants. The origin pants will remain in place, and the creature will appear in the new location wearing the destination pants. Anyone already wearing the destination pants when someone arrives via this spell is violently ejected from the pants, suffering 2d10 points of force damage. While this spell is in effect, both pairs of pants will magically shrink or enlarge to accommodate anyone with the same number of legs as the original pants. 

Troll the Dead (2nd level, evocation)

Casting Time: 1A
Range: 10 feet (and into the afterlife)
Components: V, S
Duration: Instantaneous
Casting this spell allows you to immediately mock 1 recently dead creature. The creature must have died within the last hour, and there must be some small bit left of its body for you to target. Typical castings of this spell include "Bro, do you even heal?" and "Lolz, noob!" The effects are instantaneous, in that the dead being, in whatever afterlife it has passed on to, feels appropriate shame at having died. 

Transport Via Creature (6th level, conjuration)

Casting Time: 10 min
Range: Self
Components: M (a friendly or tame creature able to carry the caster)
Duration: Concentration
The caster is able to transport himself by way of any creature in his possession that is able to carry him. This spell does not afford the creature a movement rate or type other than the creature's normal movement, and does not prevent the creature from getting tired, being hurt, or even possibly refusing to carry the caster if it chooses not to.

True Strike (3rd level, enchantment)

Casting Time: 1A
Range: 30 feet
Components: V, S (caster thrusts his fist into the air while chanting a brief slogan)
Duration: 1 minute
The caster causes 1d10 creatures of his choice to immediately cease what they are doing, form a line or march in a circle, and begin protesting for better wages and living conditions from their employers or masters. In addition, a failed Wis save means an affected creature will create a sign with a catchy slogan and hold it aloft for the duration. Anyone attempting to attack affected creatures is immediately caught up in the spell, throwing down their own weapons and creating a counter protest of their own. A creature under the sway of this spell who is targeted with Counterspell will immediately have its knees broken.

True Strike v2 (cantrip, evocation)

Casting Time: 1R
Range: 10 feet
Components: V, S (caster makes a 'gun' with fingers and points to the side)
Duration: Instantaneous
You may cast this spell as a reaction when a creature attempts to attack you, but before the to hit roll has been rolled. Casting this spell causes the attacker to attack with disadvantage. If an attacker misses three consecutive attacks due to this spell, they are 'out' and cannot attack again until 8 rounds have passed.

True Strike, v3 (4th level, evocation)

Casting Time: 1BA
Range: Self
Components: S, M (a bit of chalk dust)
Duration: 1 round
After casting this spell, if you hit with your next attack this round, the attacker and up to 9 creatures within 10 feet are all knocked to the ground (Dexterity saving throw to remain upright). However, you do not immediately deal damage to them. Your damage for this round is calculated by adding your damage dice from this round to the damage dice from your attack next round (should you hit). That damage is retroactive applied to the round when this spell was cast. The next round's damage is also applied to the round when it is rolled, as normal. For this extra damage to apply, the caster must complete the spell by enthusiastically pumping his or her fist in the air upon successfully completing the first attack. 

Wall of Dwarves (6th level, conjuration)

Casting Time: 1A
Range: 1 foot
Components: V
Duration: 10 minutes
This spell instantaneously creates a 20 foot high by 30 foot wide wall of solid dwarves. The dwarves are alive, conscious, and likely unhappy to be there. They are not carrying weapons or items of any kind other than their clothing, and none of them are spell casters. The wall will have dwarves facing in both directions, and they will immediately attempt to grab anyone within range of their arms (Dex save to avoid, Str save vs DC 18 to break free each round). The dwarves will remain part of the wall for the duration, hooked together by beard knots, belt loops, etc. Any dwarf attempting to free the wall's dwarves will be unsuccessful, and must succeed on a Str save vs DC 18 every round to avoid becoming part of the wall. Upon completion of the duration, the dwarves all disappear (with the exception of any dwarves who became caught in the wall after casting). 

Word of Recall (cantrip, evocation)

Casting Time: 1A
Range: self
Components: V, S (caster hits herself on the forehead)
Duration: 1 minute
Upon casting the spell, the caster is able, over the course of a minute, to bring to mind that word that she has been unable to...you know...it's like, recall, but...I just had it...remember!