Rainforest books and Wildlife Field Guides are a must if you are willing to enjoy the Costa Rica nature. They will enlighten you and help you to enjoy the life around your lodge or your walking trail thoroughly.
There are many, some of the rainforest books and wildlife field guides are excellent, but some of them are a mere commercial effort to get to the massive tourism arriving in our coasts and airport. My advice as a nature tour guide (And regarding the Costa Rica wildlife field guides) is to get the ones with drawings instead of pictures and to get some of the plastic ones to take on the trails.
And yes, trust me on this: you may find some for your tablet and phones. However, remember it is a rainforest, it rains. Sometimes it pours. Get the paperback, and get a transparent plastic bag and enjoy identifying what you see.
You may also find these page size laminated wildlife field guides. They only have the image and names of the animals, flowers or butterflies, and no natural history on them. If you are the type of person that likes to know about natural history to get the most out of it, also buy the guides and let these to work in the field.
Some of the best Costa Rica wildlife field guides are:
And the most classic rainforest book for serious bird watchers:
Laminated wildlife field guides:
Laminated Costa Rica wildlife field guides:
On the rainforest books
The list is long but my favorite rainforest books are:
A Neotropical Companion by John Kricher
Life Above the Jungle Floor by Perry, Donald
Life Above the Jungle Floor is funny, entertaining and quite addictive, and, it is the story of how rainforest ziplining tours started in Costa Rica first, and then in the World.