Artifact, You have no maximum hand size.
Uncommon
"Everything the wise woman learned she wrote in a book, and when the pages were black with ink, she took white ink and began again."
—Karn, silver golem
Illus. Ciruelo

10/1/2009: If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Null Profusion (an enchantment that says your maximum hand size is two) onto the battlefield and then put Spellbook onto the battlefield, you'll have no maximum hand size. However, if those permanents entered the battlefield in the opposite order, your maximum hand size would be two.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern