I've dived much of the territory this book covers, including Bali, Komodo, Raja Ampat, and Wakatobi, and in my experience the Periplus guides are about as good as they get. Just remember that one rotten reef bomber can destroy a pristine dive site in five minutes, so you can't depend on any given dive site being what this book describes. Still, you should have a book before you go there--many areas have treacherous currents (a requirement for the dazzling biodiversity we enjoy) and other tricky circumstances, so you shouldn't go unprepared.
But Indonesia has, arguably, the best diving on Earth, and this book is the best intro I know of.
One tip: Grand Komodo Tours, based in Bali, has liveaboards in many of these areas. My wife & I have gone on three of them and loved the prices and the expertise we got. Don't use expat divemasters! We only use divemasters who grew up there. You're often a long, long ways from help, and it takes locals to really know the water conditions in many of these places.
One other tip: the book recommends Tulamben in Bali for good diving, and so it is--but the divemasters at the German resort there have been grabbing all the nudibranchs they can find and moving them in front of their resort. So if you want to find nice nudibranchs there, you know where to find them now.
That's the sort of advice no book can give you--even the Periplus ones. So always supplement your book-learning with extended conversations with knowledgeable locals.
If you aren't a diver yet, try Permuteran in Bali. It seemed to have the easiest conditions.