From the intro:
"Although wizards and libraries are so often connected, very little time has been spent on exploring the function and powers of the library. Libraries usually turn up as scenic backdrops or repositories for purely magical resources, whereas there are more potentially useful books in a library than there are supplies in an adventuring gear shop. We will therefore be taking a long overdue stroll down the library aisles and finding out how to use its stored wisdom to our best advantage. Magic-using characters, who have more of a natural inclination towards reading than characters of other classes, will find an abundance of new ways to apply the knowledge set down in their books - and a whole lot of new books to go searching for!
Players of any class who prefer to use their brains as well as their sword arms will find new roles to play and new ways to tackle the challenges they encounter. Strength can see you through a tough battle, health can keep you standing when you are wounded and luck can sometimes get you out of trouble; but knowledge can trump any of these, because knowledge can find ways of applying strength more efficiently, avoiding wounds in the first place and substituting a blind trust in fate with advance planning. You will never look at a library in the same way again."