This is a 211 page instructional/reference book suitable for all levels of playing, dealing mainly with scales and modes. There's also some instruction on chord formation included(also included is a page on what polychords are and how they work). I refer to this book all the time for learning new scales or figuring out what a particular scale is. Here are the things I like most about the book: 1) there are so many scales in it, 2) I haven't seen a more complete chord naming and construction chart anywhere else, 3) there are fretboard interval maps in all keys for instantly coming up with chord fingerings, and 4) there are relative scale/mode charts for instantly finding a scales relative mode. Oh yeah, and the Circle of Fifth's is right on the cover. I recommend this book to everyone.