I enjoyed this, but even though Grann transitions smoothly between the historical parts and the sections about his own research into the past, I still just wasn't as interested in the contemporary parts. He is operating under a tough circumstance, however: the explorers went missing and there never is a truly definitive answer about their fate. While the evidence is strong, pointing in one direction, I don't think anyone can ever say 100%. And, of course, even if the theory is correct, there are no fascinating details of what happened to the three Englishmen. Which isn't Grann's fault at all, but still felt like a bit of a letdown. Like never getting to experience the (appalling and gruesome) climax of a story.
Still, it's a worthwhile read and makes me want to read more about Amazonian exploration and South American history. And eccentric English explorers of the Royal Geographic Society.