Books enable to achieve and train skills that improve the gaming in a financal, time-considering or effect-chaning way.
As soon as you possess a book you are able to use the link "use" beside the name of the book and so achieve the skill as long as you do not already have it. The training of skills does not consume gold, just time, and will be continued while you are playing or offline. Nevertheless, you are only able to train one skill at once. Sponsors are able to put two more skills to the skill training queue so they are trained right after the first training is finished.