You can get the book either from the bard mastery quest or from Hawkwind's quest, which we'll be tweaking to be more group friendly before WW.
If you select to change mastery from the book it will show you a list of the masteries you currently have, and once you select one it shows you which abilities are available to use.
If you select to change mastery from the book it will show you a list of the masteries you currently have, and once you select one it shows you which abilities are available to use.