[ploturo]

There isn't really a clean way to remove that bonus spell. The built-in spell adjustment for Fox's Cunning causes the same error.

The underlying mechanism that tracks and applies bonuses doesn't distinguish between temporary and permanent bonuses, so there isn't any way to tell how much of the current attribute is temporary or permanent when the built-in class script determines how many bonus spellbook spells should be added.

It should be possible to code the item to subtract a bonus spellbook spell, but it would do the wrong thing if another alchemical bonus was also affecting Intelligence, and it would have to be written to specifically handle each class that has some sort of ability-based bonus that shouldn't be affected (another example would be the extra starting Alchemist formulas gained).