This is awesome.
The set up is fairly science-fictional. There's a mysterious island where people go and come back insane, if they come back at all. There's a paramilitary scientific expedition to figure out what is up with the mysterious island, and there are previous ones that have never completely returned. The people who do come back are changed forever, if they survive.
Then, our main character. She's the biologist of the group, who has had problems working with others and did a lot of field work as a result. Her husband was part of previous expedition and he came back and died almost immediately after. Partly because she was affected by the loss, she signs up for a future expedition. There are others there, and the members of the expedition party are psychologically conditioned to be susceptible to suggestion so they don't panic when they cross over. The expedition is all female, so right there is an interesting break from the usual sci fi stereotype.
Then, this novel is written entirely without names. The characters are called by their job title (the biologist) or by their relationship to her if they aren't part of the team. There are mysterious goings on, a huge mystery/exploration/discovery novel and there of course is something sinister going on.
It's amazing, and there are two more books after this. They are longer and not the same narrative style, but this volume alone is worth the read of the series (which I have waiting on my to read shelf).