Spellbook of blank paper
A spellbook of blank paper can be used to write a brand new spellbook of any spell you currently know by using a magic marker. The beatitude of the resulting spellbook is affected by the beatitude of both the spellbook of blank paper and the magic marker, meaning if a cursed magic marker was to write on a blessed spellbook of blank paper, then the outcome would be an uncursed spellbook. Blank spellbooks can be acquired by blanking regular spellbooks, for example by dipping them into a fountain. A general store, a rare books store, and a second-hand bookstore sometimes have blank spellbooks for sale.
Wizards have a better chance of guessing at a spell they don't know and writing it successfully.