31 Days of Halloween: Grimoires

Grimoires, or magical books, are a tradition in European magical circles that goes back at least a thousand years (further, if one counts the Classical magical tradition). They are not merely spell books, although they do contain spells. They combine essays on esoteric knowledge, philosophy, and practical spell-casting. They were known all over Europe, from Scandinavia (where they were known as Black Books, or Cyprian books, after Cyprianus, their supposed author) to Italy and Spain. Some dealt with necromancy, some with summoning demons (a specialty known as goetia) and more mundane folk-magical practices such as the writing of magic symbols to attract love, discover the identity of thieves, etc.

I always like to have the magic books players discover in my game be more than simple spell books, and include other bits of in-game knowledge that might, or might not, be useful sometime in the future. And, since as an old-school gamer I'm all about random tables, I give you...

What’s so special about this grimoire?

1. It’s inhabited by an evil spirit that will try to get the reader to commit evil acts using the knowledge within.
2. It has a series of monster summoning spells that can only be used on one of the lower planes (Nine Hells, Hades, etc.).
3. Its binding is made of tanned halfling skin.
4. It has a version of the spell animate dead that creates special undead versions of lesser devils, but can only be used while in the Nine Hells.
5. It is written in a code that requires the use of read languages as well as read magic to make any sense of it.
6. The first half of the book has mage spells, the second half has illusionist spells.
7. It contains the formulae to create three potions (determine type randomly).
8. It appears to be a dry tome dealing with geometry as it relates to alteration magic. In reality, several high level spells are encoded in the text, and can only be discovered through intense study.
9. It is from another dimension, and contains spells that will not work in this universe. (Just wait until someone wants to buy it from you very, very badly…)
10. It is incredibly ancient, from a time when 10th and 11th level mage spells could still be cast. And it has several of them in its pages, including some with provocative names like “Ocean to Desert”, “Create Intelligent Race”, and “Destroy Moon”.
11. It appears to be an ordinary spell book, but in secret pages between its regular pages is the exact process to become a lich.
12. It is the diary of a deity from the last few months before its apotheosis into godhood. It contains profound spiritual insights.
13. It is the prayer book for a deity no one has ever heard of before. In this universe, at least.
14. It claims to have knowledge which is a mirror of reality; protective circles effective against the Angels of the Nine Hells, airy water spells that can only be cast in the air, protection from cold spells which claim to be proof against fireballs, etc. 
15. You age one year for every page you turn.
16. The book itself is sentient, and has a face on the cover that will speak to you. Its personality is… colorful.
17. It is written entirely in inked mice paw prints, like some odd type of cuneiform.
18. It is the Master Book of Law for the kingdom. Literally, as items are added or crossed out, the laws of the land change magically.
19. If you flip randomly to a page, you'll find a spell that you will absolutely need within 24 hours, no matter how unlikely it may seem.
20. It's written backwards, and even with a read magic spell requires a mirror to read properly.