It's not an easy book to summarize since it covers a lot more ground than your typical field guide. Physically it's about 8x10 inches and just over 400 pages thick. I opened the book mostly at random to take the page views so you can get a sense of what the book looks like on the inside. The photos are sharply focused and pleasing to look at; don't judge them on my reproductions. There's a few places where I have a better photo of the subject, the other 98-99% of the time the book wins.
A chapter index would have been nice to include. The first 6 chapters discuss basics of rainfall, soil ecology, plant diversity and the like. Chapter 7 is a nice discussion of plant succession which brings to life both different field studies the author wants to highlight as well as the more basic background information. Chapters 8-11 discuss speciation, evolution, co-evolution, and species diversity. What is more interesting about the neotropics than the incredible diversity of species? This section talks about how it all came to be.
Chapters 12-14 discuss specific ecosystems, divided into wet, high elevation, and dry sections. It looks at specific plants, animals, and (predominantly) birds that are unique, characteristic, or simply an interesting element of their diverse surroundings.
The bottom line is that if you are going to the neotropics, there's a ton of information here that your guide is likely not going to have time to discuss (or know); you will enjoy your trip more even if you just thumbing through this book and reading it little paragraphs or sections at a time.
And the requisite disclaimer: Princeton sent me a free review copy of the book though they've never asked to see what I wrote about it.