I took this book with me to Costa Rica so that I could spot and identify commonly-seen birds and wildlife there.
The first part of the book contains an overview about Eco-traveling that could have been summarized a bit more. The book conveniently places details about wildlife in the center of the book, and puts the illustrations in the back so that you can do faster lookups.
Although I appreciate the emphasis on Eco-travel, I found this book rather disappointing when used as a reference. Some of the birds I saw more than once were not listed at all. There are few illustrations of what the birds look like in flight and there is little about age- or gender-based differences in appearance. Also, although the wildlife coverage is fairly good for reptiles and amphibians, there is very little about marine or plant life.
I'm still relatively new to birding, but if I could do it again, I would have paid the additional cost and bought the Stiles and Skutch book.... If you're not a bird watcher and you're just looking for a basic 'wild life' identifier, I would suggest skipping the book, and instead, buying one of those laminated 'bird/wildlife identification' cards that you can find for about $10 in many of the visitor-oriented shops around Costa Rica.