You find a spell book! It has nothing you don't already have <boo>. But you find in the very back a page written in a different style, and the page itself is perforated (or not). What you have found is a essentially a spell with all the properties of a scroll, but on an page. One time use, but maybe it isn't a spell copyable into a spell book at all (homebrew maybe).

Was thinking of using this concept for a book a player's wizard had found. Thoughts?

Spellbook and scroll can be interchangeable. A scroll can be copied (and its magic transferred) into a spellbook, or added to a loose folio of spells. Likewise, a Wizard can cast directly from a spellbook, thus erasing the spell from the spellbook. (This is different from preparing an "open slot", that reserves a spell slot so as to cast from the spellbook safely.)

This approach is less vital in 5e, because Wizards choose a substantial number of new spells while leveling, and can cast their prepared spells, spontaneously. Even so, spellbook=scroll remains a viable option.

Quote from Gvarayi >>

Likewise, a Wizard can cast directly from a spellbook, thus erasing the spell from the spellbook.

 Where is this rule present in 5E?

Quote from Farling >>

Quote from Gvarayi >>

Likewise, a Wizard can cast directly from a spellbook, thus erasing the spell from the spellbook.

 Where is this rule present in 5E?

Homebrew, from previous editions. I didnt mean to imply it was 5e legal. Just pointing out, it is balanced.

I see nothing wrong with this as long as it's not used to trick the player -- make sure the player knows. What I mean is, don't tell him/her "Oops, you read it, the spell is cast and you lose access to it forever." Make sure the player knows that it's a single-use spell.

I like Gvaryi's idea, though I too thought they were making a 5e rules statement that had me going "huh?"  I think I'm going to work that into my game too.  

In my game I sort of unbind "magic writing" from books and scrolls.  For instance, one's magic book could be something like an abacus or a staff with your spells inscribed therein, etc. (In my game world "magic books" and other magic media aren't really so much a spells on a page but each book or medium is a guide to a Wizards understanding of magic broadly and the study notes are used to deterime their understanding of certain spells). It's one of the reason I like the magic tattoos because it opens the door in RAW for magic to actually be written on the body in some way.

Anyway that's all to say I kinda like the idea of perforated spellbooks, but would instead propose a magic item where a thinner, softer texture of paper is wrapped about a tube, and the caster can cast randomly determined magic as they tear off squares.  Magic toilet paper basically.

Yeah, I'd prefer if you want to deviate from the way scrolls work it's best to use a whole new medium altogether. It gets weird having to explain to the wizard why they can't copy this particular spell even though a key part of the class is being able to copy spells... kind of feels like you're purposely circumventing their features. But make it a tattoo or inscribed item or magic biscuits or whatever and there's no issue.

One reason is that we are not really doing the spell book to get spells setup for the wizard, it’s more like a sorcerer. So finding spellbooks doesn’t  mean as much and I thought this might be a nice idea to find an item of interest in the book. 

I’ve watched Caleb from Critical Role and though they play it a bit that way, for the most part Matt just allows him to get any spell, at least more so as they have level up. 

I guess I could just say it’s a scroll that was stuck between pages within the spell book.