Cavegirl Gamer's OSR Dueling

 Years behind, but just found this gem:

HERE

About The Spellbook of The Mage You Killed...

 1 Tome goes up in flames

2 Tome goes sentient, flies around (as harpy, destroyed if HP zero)

3 Tome backfires as a curse shaped by the spell cast

4 Tome is sucked into a daemonic vortex, PCs trying to grab it must travel to hell and fight a suitable demon

5 Tome pages come apart with owner's death, each spell being a scroll that cannot be copied, only cast once

6 Tome becomes a Grimoire Golem (as Paper Golem) that either attacks any spellcaster nearby or wanders off to find one. The tome of any spellcaster killed by the golem becomes another golem.

7 Tome becomes a Spellbook Mimic (as Mimic but immune to magic) and gets a surprise attack on any trying to touch it

8 Tome is cursed, rewrites over the spellbook of any nearby magic user. If none are nearby, the ink oozes out and it becomes a useless wad of paper.

9 Tome sinks into ground, creating a magic funhouse dungeon with as many levels as the highest spell it held

10 Tome is locked by magic requiring a side quest to remove