Tone down the 'well prepared' Tome of Donors effect
This effect grants resistance to paralysis, confusion, death rays, fire, cold, and acid. Paralysis resistance on its own is highly desirable for the entire game, paralysis being the most common "instant death" status. Confusion resistance is useful for two required bosses, and is otherwise impossible to get intrinsically. Resistance to death rays is not relevant for most of the game and is available from guaranteed equipment, but having it intrinsically still allows you to use better equipment when it is relevant. Elemental resistances, while available from many sources, are very useful and de-fang many early-mid-game threats.
As a package, this set of resistances is extremely powerful and greatly reduces the threat of dying in both the short and long term. While all the Tome effects are basically free bonuses, I think this goes too far and makes the game too easy. I would suggest having the effect give the PC a random one of these six intrinsics that they don't already have. This makes the effect more reasonable, while keeping a chance to win the paralysis resistance jackpot, and making the effect not a let-down when it is received multiple times.