To start with the positives, which are exceptionally well done: Lily King creates an intense, stifling, and deeply unsettling environment; the mud, the stench, the sweat, and the physical discomfort are visceral and suffocating. Much of her research is precise, and the anthropological details are fascinating. Her imagery is striking, and Nell/Mead is indeed an enigmatic presence.
Nevertheless, I was nagged by several issues. As a narrator, Bankson's a not-terribly-interesting outsider, even given his past tragedies and recent suicide attempt; they're simply a list of facts, sad things that happened at some point, but his emotional state isn't fully developed - he is largely concerned only with Nell. Fen is such a brutal, avaricious villain that there's no surprise in Nell's preference for the company and conversation of Bankson, who (unjealously) respects her mind and treats her kindly, so the love triangle didn't hold much tension.
Rather than letting the reader get to know Nell, her thoughts are filled in by her journal, which finds itself in Bankson's possession years later. It felt contrived, a way to fill in lots of information and Nell's plain thoughts, but only to an extent; she writes that she's in love with Bankson, erasing some needed tension, but she leaves out the part where she's being violently beaten by her brutish husband, a fact made clear to the reader long before it seems to dawn - too late - on Bankson.
The focus on anthropology, while fascinating, bothered me in places as well and contains perhaps my biggest quibble. We see how starkly out-of-place the three observers are - particularly Nell and Fen, with their crates upon crates of possessions - and how arrogantly biased, clearly reaching specious conclusions and projecting their own self-serving theories. While we're shown how little the anthropologists truly understand about the natives, however, I'm not sure the novel itself fares much better - they serve here only to better investigate the protagonists. They're scenery. None are real characters, which is most glaring with the almost completely unspeaking Xambun, who sets much of the last third of the book in motion. His death is key to the story, but, as a man and as a character, he's written as utterly expendable. We're told of the emotional cost to Nell and Bankson, but it doesn't resonate with a reader who has barely been acquainted with him The environment remains exotic and threatening, a backdrop to a larger story.
While I understand it's a personal preference and, to many readers, utterly beside the point...why bother with a meticulous focus on Margaret Mead's years in New Guinea, with characters so clearly based on the interactions of Mead with Reo Fortune, Gregory Bateson, and Ruth Benedict, when the ending was entirely fictionalized? King states elsewhere that she "had slipped out of the shackles of history, made a clean break with fact. And I set off into the jungle of my imagination," and that "A novel is where I want to feel the truth. Sometimes you need facts to get at the truth; more often you need your own voice and vision." I can respect that, but, to me, it didn't feel true - it felt like a twist of an ending that went for shock and Lifetime-movie tragedy at the expense of truth.