Okay, so there is a book 3 and a book 2 but why not a book 1? Here is what i think 'bout the different books.
Book 1: Magic Spells
Book 2: Artifacts and/or relics
Book 3: Monsters
There might even be a fourth and a fifth.
Book 4: Alchmey
Book 5: Enchanting machinery
I have good reason for this threory:
Book 1: Well there not going to have a book 2 & 3 with out a book 1, and shouldn't you start magic training with spells?
Book 2: Gideon had an amulet which would be a magical artifact
Book 3: Its kinda obvious.
Book 4: The potion Old Man McGucket gave Dipper and whatever enchanted the wax figures, but the major factor is the "meaningless decorations" on the books seen. That deco is a bunch of alchemy symbols.
Book 5: Copy/cloneing machine, the mechanical Gobblewonker, and that carpet thing, also that vending machine that Stan disappeared into at the end of episode one (but thats less magic than technology)
All in all, i'm wondering when a charater is going to show up that can clue Dipper into the rest of the plot.