I have been hoping for a long time to get to Costa Rica for some outstanding birding. I purchased this book after reading other positive reviews and I'm very glad I did. This book gave us the information and the confidence to schedule a three week trip in 2010 that includes the Caribbean Slope, the mountains, the Pacific slope, and the Pacific Coast. Detailed, current, and right to the point. Great maps, driving directions, bird lists, and pointers. Our kudos and thanks to the author.
Update: We just came back from our 20 day trip to five different Costa Rica locations! We had a wonderful time. We saw 188 species of birds, explored mountains, remote beaches (including Corcovado), and various rain forest habitats. I can definitively say that the reason everything went so smoothly was in part because of the detail, thoroughness and accuracy of this book. Even if you are going on a guided trip arranged for you by someone else, I would read and bring this book!