
Probably the best point of the book was how interweaving Fawcett's and Grann's story allowed Fawcett to slowly come into the foreground; in the beginning, he looks like a quietly competent man, the last of the Victorian era explorers. By the end, he seems like a madman on a spiritual, rather than a scientific, quest. The weakest point was that the long winding up was unable to produce a satisfying conclusion -- Grann spends the entire book working up to his Amazon trip, and then nearly immediately comes to a conclusion. While he's able to tie this in with the end of Fawcett's story, it feels rushed, pat, and not fleshed out. (Of course, given that Fawcett disappeared ~80 years before Grann began the project, in a jungle, Grann was unlikely to find anything other than he did, which is old Indian legends).
Overall, this is a fun pop-archaeology/anthropology/history book, with an interesting hook.