Book
Type
Cost
25 gp
Weight
5 lbs
A book might contain poetry, historical accounts, information pertaining to a particular field of lore, diagrams and notes on gnomish contraptions, or just about anything else that can be represented using text or pictures. A book of spells is a spellbook (described later in this section). Any book of masterwork quality covers in detail one specialty (see Specialties on page 408 in Chapter 6: Using Ability Scores). You gain an expertise die on checks made regarding the specialty detailed in the last masterwork book you’ve read.
Source