Preservation rituals seem few and far between, but would gentle repose work? It's usually used on corpses but it is at heart a method of slowing entropy increase.
I am not going to say that you can't use Gentle Repose, but I won't say that the book will be fine and dandy if you do decide to use it. Like you said, it is only used for people, so you don't know the effects it might have on a book, if anything at all.
Irish Avatar by Savannah
Tak, Half-Orc Slayer
Garr, Human Barbarian
Thornin, Dwarf Fighter
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Odin, Dwarven Cleric of Moradin
Necia, Half-Orc Monk