Don't Starve recently had an update which added Books for Wickerbottom, the Librarian.
These books have various effects, some of which are really pretty over-powered. Her ability to instantly grow plants and farms, and her ability to summon Tentacles, both stand out as incredibly game breaking. Given the expensive cost of books (reeds being a risky venture to acquire), I'm curious if it's a one-time use, or if you keep that book permanently.
Are books a one-time use, permanent, or do they degrade over time?