Everyman Chess has been putting out books in the "Dangerous Weapons" series for a few years now, and they're deservedly popular. It's in the same genre as New in Chess's "Secrets of Opening Surprises"; to wit, an effort to offer surprise weapons (that might be the name of some third publisher's series, borrowing one word from each of the two competitors) in mostly mainstream openings. The lines are not intended to be one-off throwaways, garbage lines that can only work by relying on the opponent's ignorance. Rather, the aim is to play sound, interesting lines that are either new and not yet well-known, or known but relatively unexplored. These lines generally have a special drop of poison (they are supposed to be "dangerous weapons", after all [are there "benign" weapons?]), but not always - sometimes they are worthy alternatives but aren't laden with any specially trappy ideas.
Turning to the volume at hand, on the King's Indian, Richard Palliser, Glenn Flear and Yelena Dembo have put together a collection of 14 chapters focusing on 7 different variations of the King's Indian. While main lines in the broad sense are certainly covered, you won't find any discussion of super-theoretical lines like the Bayonet Attack or the 9.Nd2 Classical we've seen in the recent Beliavsky-Nakamura and Gelfand-Nakamura games. On the other hand, whether you play the King's Indian or play against it, this book will give you options before you have to worry about the aforementioned variations.
This brings up another point, typical of this series: "weapons" are offered to both sides. While nine chapters are written from Black's point of view, that still leaves five chapters trying to help White. Further, from what I've seen so far, the authors are pretty fair. In lines intended for Black, the best White tries are discussed, and in at least one "Black" chapter the author acknowledges that White probably enjoys a small pull with best play from both sides.
I've liked what I've seen so far, both of the series in general and this volume in particular. While I'll repeat my general advice that players under 1800 shouldn't worry too much about openings, except in a very general way, and focus on tactics and endgames, those who are interested in the King's Indian with either color but want to avoid tons of theory may want to investigate this book. (If you go here, you can get more information and download a sample in PGN.)