Chasm City

This book is a bit of a whirlwind with main characters that shift and weave through the book, while always remaining interesting. The SF concepts are extremely interesting and one of the major themes of the book is immortality. Specifically, how long would you have to live and how much good would you have to do to overcome some amount of evil you did early in your life.
The author does a great job of changing your perception on the characters in the second half of the book, which may be jarring for some. I can't say much more about that without major spoilers. But it is done well and actually in a plausible way, given the constraints of his universe. Speaking of which, his universe is very broad and well thought-out. There are aliens who are very nearly incomprehensible, but still quite interesting. Relativistic space travel is also considered throughout the book with generation ships featuring throughout.

In the end, I highly recommend this book. I wish I had read it before Revelation space and will need to go back and re-read that one now to see if it is more digestible on the 2nd time around.