I joined spellbooks together, which was ok to create, but the resulting spellbook is "too expensive" to ever use on anything. The "too expensive!" should take place when creating the spellbooks, or the stupid and illogical limitations on your own creations be removed.

My Minecraft is unedited and hacked, though has gone through many minecraft versions while playing. Spells in the "too expensive!" book to use are:

Impaling IV

Unbreaking III

Mending

Protection IV