I've been searching through D&D videos on YouTube and examining varies forums, but have yet to find any really discussion of the Pact of the Tome Warlock.

For my present character, the spin that I am using is that their fiendish patron wants the warlock to serve as a kind of priest for their cult... so the cantrips gained where 'Produce Flame', 'Sacred Flame', and 'Spare the Dying'. At 5th level I'll pick up the Invocation 'Book of Ancient Secrets' and take the rituals Ceremony and either Find Familiar or Purify Food and Drink.

I'm curious what others think of the Tomelock

It seems like the most versatile option to me, as long as you use Book of Ancient Secrets and can get decent access to ritual spells via scrolls or spell books or other means throughout your campaign.

Ritual spells offer a TON of utility and you can access them all, from any class, without using a precious spell slot, for a mere +10 minutes casting time!

I'm a huge fan of taking Shillelagh (Druid) and Guidance (Cleric).

Guidance helps on most actions in the Exploration phase.

Shillelagh means your warlock's staff is now a deadly weapon.

I live the Pace of the Tome, but it's an expensive class.  Scrolls in this version are very not cheap, then you pay to scribe it.

In many ways it feels like the "default" option - taking Shillelagh as one of your cantrips is probably more useful for non-Hexblades than Pact of the Blade, and once you get your ritual invocation you can also cast Find Familiar and get most of the features of the Pact of the Chain too. On the other hand, it's maybe a bit less flavourful than the other two. Hexblades are almost all going to take Pact of the Blade unless they're ignoring weapons and just using it for armor and cursing, and you do admittedly miss out on invisible, magic-resistant minions of the Chain Pact and the decent invocations that come along with them. Having extra cantrips and rituals means a lot more utility though, especially if your party is missing a Wizard and/or you don't get a lot of short rests to replenish your spell slots.

Pact of the tome is very useful when you're the party's lone caster or perhaps one of two where the other one is a Divine caster. I love the diversity of cantrips, and how you use your tome can be excellent roleplaying flavor. For example, my DM makes me record everything I encounter of a magical nature as soon as I can after the encounter, including drawing. For that reason, I took eyes of the Runekeeper. Eventually, I dropped it when I learned to cast it as a ritual with the book of ancient secrets invocation. The DM let me keep Eyes of the Runekeeper as the ritual spell. The ability to swap out spells and invocations as you level up is the inherent advantage, along with short rests that refresh your slots. In concert with your Tomelock and Book of ancient secrets, you become a really good Swiss army knife in many situations.

Tomelocks are all around good due to the versatility but are especially good if you need a full caster in the party.

As in, you have a Paladin, Ranger, and Fighter. Sure Paladin's and Ranger's can cast spells, but not like you can! The access to rituals you can get makes you competitive with other "Full Caster" types in the game. Especially since your spell slots charge on a short rest, you can swap around invocations, learn rituals from any class, etc. 

They're an all around good pick, but get even more useful when you have party that's more martial and less magical. 

I may be biased but they are my favorite type of Warlock too ^^'

Tomelocks work in really well as a multiclass option as well. I recently multiclassed into Warlock with my Vengeance Paladin (level 8) and took Celestial Warlock (level 5 now) with Pact of the Tome for additional spells, rituals, and cantrips for utility. It has reeeeaaaallllyyyy helped out the two casters in my party with their ability to be more flexible with their own spell slots and has allowed one to specialize in being a full-on blaster since I could shift a few spells and cantrips around so they weren't stuck doing things they didn't really need to be doing. The Aspect of the Moon Invocation (probably one of my favorites overall) which has a prerequisite for Pact of the Tome has essentially gotten rid of the need for us to take turns during resting/sleeping periods too! You don't need sleep, can't be forced to sleep, and gain the benefits of a long rest by keeping watch or doing light activity with that Invocation!

Tomelocks are great, but it might vary on how you play them. If you don't make use of your cantrips then it is a waste. Tomelocks might be even better than blade and chain(as Ratwhowouldbeking stated)shillelagh rplacement for a bladelock(although you do miss out on cantrips) if you wanted to go that style,  with still two extra cantrips and you could take book of Ancient secrets with find familiar for a replacement for a chainlock.

Quote from Mael >>

It seems like the most versatile option to me, as long as you use Book of Ancient Secrets and can get decent access to ritual spells via scrolls or spell books or other means throughout your campaign.

Ritual spells offer a TON of utility and you can access them all, from any class, without using a precious spell slot, for a mere +10 minutes casting time!

 When I was thinking up my character concept, I was considering Pact of the Tome, but my DM is pretty stingy with magic items.

If you can't gain access to scrolls or spell books with ritual spells, you're SOL. And even if you can get your hands on those items occcasionally, what is the chance that it will contain a ritual spell...

Further, after you reach 3rd level or higher, cantrips lose their shine.

That's why I went with pact of the chain.

Quote from Grunk999 >

 When I was thinking up my character concept, I was considering Pact of the Tome, but my DM is pretty stingy with magic items.

If you can't gain access to scrolls or spell books with ritual spells, you're SOL. And even if you can get your hands on those items occcasionally, what is the chance that it will contain a ritual spell...

Further, after you reach 3rd level or higher, cantrips lose their shine.

That's why I went with pact of the chain.

 Depends on your cantrips and how you use them. I find Ray of Frost to be useful and I'm 6th. Thaumaturgy and Prestidigitation are also useful in a setting where you can get opponents off their game.

Also, ritual spells aren't just gotten from magic items. Your magic is learned from or with your patron. So, if your patron sees you in a new environment, like a marine adventure, he or she may choose to Grant you water walking or similar, as the situation allows, after you've earned it over the course of episode one. That relationship is key to your magic and if the Tomelock was limited by the DM's choices of magic items, then maybe you can work a way that skillful situatiobal roleplaying becomes a method of earning ritual spells 

I have an absolutely fun meme build I love to run for a tomelock that only takes 5 levels. It's well suited for multiclassing so far that I've run into. You take the fiend patron. Grab poison spray, eldritch blast and chill touch. Then with your tome grab: acid splash, Thunderclap and personally I grab toll of the dead. For the invocations I grabbed agonizing blast, eldritch spear and fun for I grabbed one with shadows. With level 5 you can grab the feat spellsniper which does wonders. You ignore half/three-quarters cover it doubles the ranges of cantrips and grants you a seventh cantrip in which I grab flame bolt. And the end result is acid splash and poison spray have a range of 60ft. Flame bolt and chill touch have a range of 240ft and eldritch blast has a range 600ft and all can ignore most forms of cover