Hyperion by Dan Simmons
It was a long time since I read this book, and to be honest, I don't remember enough plot details to discuss its finer points. However, I do remember that I more or less devoured it, and that it has a very interesting structure.
Basically it is a set of different histories told by a number of strangers as they make a sort of pilgrimage to a planet hosting what seems to be the most horrible thing in the universe. They know that there must be traitors among them, and so Hyperion is also a kind of detective story. It is the first part in a series, and one can feel that from the somewhat abrupt ending.
In any case, the bottom line is that I found Hyperion well written, entertaining, and worth recommending.