Spell books become so imbued with energy from mental focus that they obtain a kind of magical life force of their own. Unlike magic swords though, this force isn’t strong enough to also support any recognizable intelligence - the already heavy burden of holding spells and their glyphs makes such physically weak constructs unable to bear more. Historically, this matter has been debated within the magic using community - but every time an independent intelligence was thought to exist in a magic tome, it’s been demonstrated that an illusion or external agent of some sort was to blame. Nevertheless, there are still some wizards in more rural areas who insist that they’ve seen intelligent spell books, or even that they can converse with their own. It’s a reminder of the sad fact that many who should never have taken up the profession of magic user in the first place persevere to the point of madness.
A detailed and well documented investigation made ages ago by the archmage Fenrond into the phenomena that occur at the moment of a spell book’s destruction is what led to the discovery of their life force. Fenrond was able to astrally observe and follow the essence of these tomes to the plane of Nirvana, where certain modrons catalog and file them away. Others have since repeated the journey, and thus it’s now known that no spell ever inscribed in a spell book is truly lost - though the method behind the modrons’ filing system remains indecipherable.
Therefore, spell books can be said to die… From old age and neglect, from fire or excessive water damage, from being shot through by arrow or pierced by sword, etc. Fenrond’s original writings on the subject are still added to by today’s mages, who continue to document the effects of the (so far) unpredictable release and conversion of energy which occurs on the so-called Prime Material plane at the moment of a spell book's demise. A small number of these are listed below as examples...
1. Everyone within 30’ of the book forgets (and will be unable to retain) their name and anyone else’s in range, for a number of days equal to the highest level spell that was in the book. There’s a 5% chance of never remembering one’s own name and having to make up a new one.
2. The book simply explodes, causing d6 (+1 hp for each level of spell contained) concussive damage to all within 10’.
3. A Stinking Cloud spell effects all within 10’ of the book when it expires.
4. Any intact pages of the book will tear free and flutter around a 20’ area causing confusion and -1 on to hit rolls for one turn.
5. A Slow spell effects all within 10’.
6. Everyone within 30’ is filled with the overwhelming desire to compose rhyming verse appropriate to the surroundings, and will be unable to perform other actions until at least four original lines of such are spoken.
7. Light or Darkness (per the spell) emanates from the last resting place of the book, depending on whether the book’s last owner was good or evil, accompanied by the sound of harps or funeral music respectively.
8. Amidst sparks and smoke, a random spell from the book is cast into the immediate area of the book with a random target being chosen (if appropriate).
9. The ink literally jumps from the pages of the book to become a small host of Inky Slinkers.
10. A random spell from the book supplants one in another spell book in the vicinity. If no other spell book is in the area, than it supplants one on a scroll. If neither are found in the area, a Bronx cheer is heard.