This is a weird one because it's a good example of a bad book written by a clearly competent author. Somehow this rankles me more than a plainly bad book. It was perfectly readable and the descriptions of the environment, sailing, interactions, etc were good. Beyond that however it just didn't emotionally connect at all. The other reviews that mention deeply unlikable characters, cringe themes of white fragility, pacing issues, uncomplicated complications, all make very good points. 

Overarching all of it, for me, is that I could not buy into the mystery and romance and passion of the place or the characters. That is the fundament you need to build up for the 'downfall' to feel meaningful in this kind of story. Instead of comparing it to The Ruins, as other reviewers have done, I think of The Island, which follows the same basic pattern. That book works because it really makes you believe in the (at least the character's) dream of the place - the holy grail! It makes you believe in the character's relationship to it as part of his life's journey, how that relates to the reader's life journey, how this relates to how humanity idealises "unspoiled" places and how seeking necessarily spoils. That's why everything that happens afterwards hurts so much. This book made me feel none of that, and so everything fell flat. I'm sorry!