Xp Tomes are magical books that use your XP level as a form of mana.
To craft these, you first craft a normal XP tome by putting a book in the center of the crafting table, with 4 bottles of enchanting to its orthogonals. It also requires 2 quartz blocks to the bottom left and top right grid, with amethyst blocks filling the other diagonals.
The normal XP tome has no effect, but is instead used as the central crafting ingredient for the rest of the tomes, which are left for you to discover.
(Note: the internal names of everything in this mod use totems instead of tomes)