Your maximum hand size is increased by one. The scrollkeepers never stepped an inch away from the doors of the Great Library, not even when the ogres and their oni masters swept through Minamo.
Illus. Paolo Parente
10/1/2009: If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Minamo Scrollkeeper (an enchantment that says your maximum hand size is two) onto the battlefield and then put Trusted Advisor onto the battlefield, your maximum hand size will be three. However, if those permanents entered the battlefield in the opposite order, your maximum hand size would be two.