There are a number of excellent books on Knotting available, but I want to recommend two: one that you can carry in your pocket, and another that will pass MANY hours when the weather keeps you inside instead of out building structures.
Collin's Gem guides are pretty useful pocket-size guidebooks. The Collin's Gem: Knots book is particularly good, covering most of the essential knots and one or two of the more unusual ones.
Once you have mastered the Jury Masthead and the Matthew Walker knot and want to move on to bigger challenges, then you need to look at Ashley's Book of Knots. Clifford Ashley spent literally decades writing this book- at the time it was published, practically every single knot known at the time was in this book. In fact, most knots can be referred to by their illustration number in Ashley's (sometimes abbreviated to ABOK). Other than a number of knots that have been invented in the last 50 years (mostly climbing knots), everything you need to know about knotting is in this book.
(click on any of the links to buy the books at Amazon.com)