Spellbooks in D&D can be boring. We live in such a book-rich society, with the printing press and cheap paperbacks and libraries and bookstores, that we forget that at once upon a time the proper reaction was probably more like holy crap! you own a book! The pre-Gutenberg codex was a work of art, requiring intensive labor to produce. In some instances they were literally chained to the desk where you would read them, in order to prevent theft of these valuable resources. For certain milieus a filthy adventurer owning a book is kinda like going over to your buddy's crappy studio apartment and seeing an original Picasso on the wall. Not utterly impossible, but it makes you want to ask impolite questions like "Is the rest of your stuff cheap junk because you spend all your money on your art obsession?" or "Hey, man, are you some kind of international art thief?"
That's why for my next go at my 12th century faux-England campaign I've decided that spellbooks are basically artifact type objects rather than the users manuals for arcane systems operators they tend to come off as. The Call of Cthulhu tome rules and Ed Greenwood's "Pages from the Mages" series in Dragon heavily influenced this decision. As did reading a couple real historical grimoires, the problems surrounding the textual transmission of the works of Shakespeare, unearthed manuscripts like the Dead Sea Scrolls and Nag Hammadi Library, and the enigma of the Voynich Manuscript.
So now I've got a spreadsheet I've been working on, with the goal that each spellbook can be treated as an individual object. Here are the current fields, with some comments:
alt name - Many of these books have more than one name, which makes tracking them down a big ol' pain in the butt.
language - I don't use read magic for spellbooks. Instead that spell "unlocks" scrolls and doubles as identify for any magic item that has runes on it. I think OD&D will back up this interpretation.
past owners - "Your spellbook was once owned by Merlin." How cool is that?
blasphemy - Spellbooks aren't strictly how-to guides written in a vacuum. Each comes with a context that a canny reader can puzzle out. And since pretty much all wizards are cranks, heretics, pagans and/or crazies, this means that one or more passages or implications in a spellbook will offend the sensibilities of the strictly orthodox and question the worldview of the open minded. The historical nature of my campaign makes this a lot easier to pull off effectively, I suspect. In a totally made-up world you're going to have to work hard to come up with a convincing blasphemy. In Wessex I can get away with things like "The Holy Spirit is a woman, God's wife and Christ's mother" or "Satan isn't a rebel, he's God's double agent." My only concern is that the World of Darkness probably ran this sort of stuff into the ground, making it completely uninteresting to Vampire fans.
comment - vague catchall
Spell 6 - Capping level advancement to 10th means I can get away with pretty short lists of spells. Just to make life rough for the PCs, fireball will only be appearing in a single grimoire, which starts in the hands of one of the active NPC wizards. (Active NPC wizards have their own file.)
My list of grimoires is approaching 40 total entries, though none are totally complete yet. That's probably way more than I would need for any one campaign. Eventually I want to be able to hand starting M-Us a print-out of their initial spellbook with all this cool info on it.