While at first look this book may seem very well-written and detailed, describing many remote regions of Indonesia that other guidebooks ignore, much of the description of such remote places is obviously based on hearsay.
When visiting many of those remoter islands/regions during my 4 years around Indonesia, I very often found that the exciting attractions (like traditional architecture or traditional cultures) described by this book simply did not exist!
While the background information on better-known parts of the country is more accurate and worth reading, the fact that many parts of this book don't seem to have been updated for decades further reduces its value.
So I'd say that for background information the regional guides by Periplus are better, while for practical travel details get the Lonely Planet or Rough Guide.