Too Limiting for a field guide
I found this book only really useful for mammals. I had to supplement this book for amphibians, reptiles, and especially for birds. I found it is really only good for 'popular species' of the non-mammals. If you are a casual naturalist and only want to bring one book, it is ok, but if you trying to really id a lot of organisms and add to your life-list, this isn't a great book.

Overall a good book
Overall, I think this is a good book. It provides good descriptions and illustrations for identification. I also liked that it included the parks and habitats where each of the species could be found. I was a little disappointed by the organization of the book (how the information is separate from the pictures). It is helpful when trying to quickly trying to ID an animal to have all the pictures in one spot, but it is a pain to have to flip back and forth to find out any facts. I was also wish that some butterfly species were included in this book.

Best Costa Rica bird guide written
We are going to Costa Rica this SPring and this book has been the most helpful guide in preparing for this trip.

Good news and bad news
I just returned from 10 days in CR and bought this guide (under seal so I could not examine it before purchasing) when I arrived there. This guide is great in that is provides wonderful data on amphibians, reptiles, birds and mammals and lots of information on CR geography, conservation, ecology and related. The guides I met really like the book for the "friendliness" of the presentation. Unfortunately I found the book to be cumbersome because it separated the animal data from the plates and the book lacked cross-referencing, so there was a lot of back and forth trying to read about something then find its illustration. Also, the book is very limited in the varieties of each type of animal. Since my main interest is birding, I was very frustrated not to find many of the birds I was seeing. Lastly, I paid $48 for this book when I arrived in CR and later I saw it for $38; state-side the book sells for $20 or so. I think it is a wonderful overview book on animals of CR but I do not recommend it as a field guide.

Costa Rica Guide Book
Les Beletsky's "Costa Rica (Traveller's Wildlife Guide)" was a delightful and much-used companion on our recent tour in Costa Rica; and we are still reading it, now that we are home. Since we are especially interested in wildlife, we really enjoyed the beautiful, clear bird and animal illustrations and descriptions. We carried it with us on every bus and boat excursion, and it enabled us to identify many of the birds we saw. We found the comments about the parks and ecosystems in which the animals can be found to be very helpful.
The only shortcoming is that the plant descriptions are so brief and the plant illustrations are not in color.
The habitat photos are outstanding. Looking at them reminds us of the amazing variety of scenery we saw in Costa Rica.