Passage by Connie Willis, 2001.
If, as I recommend, you choose to pick up this book, don't read the blurb on the back. It may reveal too much.
Two scientists study near-death experiences. The book does a lot right. The attitudes toward death ring true. The characters ring true, mostly. The plot is interesting, the writing thrilling, the portrait of humanity immensely gratifying, the emotional range fantastic.
A certain extended metaphor, which I won't reveal much about, figures centrally in Passage. But only the symbolic side of the metaphor is revealed at first, and its real-world analogue is hidden. The meaning of the metaphor is the central mystery of the book, and it's a clever one. So far, so good. But there are a few problems with the book.
One is that the metaphor Ms Willis chose is, through no fault of hers, rather overexposed as metaphors go.
But the main problem is that Connie Willis is too much a character in this book. Death is a marvelous mirror; in it we each see our own beliefs about the fundamental nature of the universe. Ms Willis's own views come through quite clearly in Passage, and her portrayal of other views unfortunately doesn't bear the same verisimilitude as the rest of the book. It would have been possible for the protagonist, a scientist, to despise her unscientific counterpart without Ms Willis piling on. Similarly, too much of the suspense in reading the book is due to the question of where the author is going. One wonders whether the book will maintain its hard-nosed scientific attitude to the bitter end; whether the author will ultimately try to give some kind of answer to the question of the experience of death, which hangs over the entire story; and so on.
Still, a hell of an effort by the reigning champ of science fiction novelry.