Is there a book with +2 Spellcraft?
I saw several threads (not sure if here or over in the Grimrock forums) mentioning it in the optimal build threads: "Leave Spellcraft just 2 points under your target value because there will be a +2 Spellcraft tome."

I'm on level 9 and found none so far.

So is it there? Was it patched out? Have I overlooked something? Is it the Fire Tome? That one has +3 Fire Magic, +1x Fire Resistance.

There are a couple of Tomes of Infinite Wisdom in the game. Those are not very infinite, since they only give +5 skillpoints, but you can assign those to anything you like - including Spellcraft.

I'm not aware of a specific +2 'specific skill' book, though.