Books skills (Divinity: Original Sin 2)

Players want to ask a few questions on the topic.
Books skills somewhere across multiple copies/duplicated from the merchants in the game?
As better junk to do. Several craft of unknown skill? And how it is unknown?)) For example Fire + Necromancy = corpse Explosion ....but corpse explosion, and so comes across as a separate book.....In short I have bought a few books,but to me the toad smothers to give them to the lizard(I want to break up with him-goat all shore beguiled). Can I have that thread gash worthwhile,not found in the game?
here in the screenshot -dialog with the boy in the cave(pulls out spear)...that he gave us? he saw where his treasure/reward?