If you've heard of Ted Greene's books, chances are it's Chord Chemistry you've heard discussed. This book is a complete departure from the style of Chord Chemistry and it's overwhelming array of chords. I think this book is a "must have" for all ranges of guitarist.
This book is one of a very few guitar books that will teach you through your ears. It provides masses of instantly pleasing chord progressions. Very little or no analysis of the progression beyond the roman numerals for the chords.
For me, it is best used as a reference, dip in at any page, play the progression.. if you like it play around with it, try the alternate suggestions. Good progressions stick in your mind you start hearing the other chords you'd put in or personal touches. I've picked up the book and played my own variations of a progression for whole afternoons.. finding one pop song after another that use those chords.
Just like Chord Chemistry there are years of value in this book, but it is so much more accessible. Chord Chemistry is an unabashed slog, this is a completely different beast. Of all the theory and tab books I own, this is the only one I will not part with.
After a while chord progressions start slipping into tunes, replacing 2 chords with 5, and sounding tasteful.
Downsides? I guess a more rigid indexing of the progressions would be good, so it could be used as a "cook book" but while this book would always get you out of scrapes where you need to fill, the real joy is in finding out you can recall a whole bunch of chords and substitute them in effortlessly.
An excellent reference.