I am conflicted by this book. On the one hand, Reynolds brilliantly imagines far-future human societies (like the genetically modified space-faring Ultras), giant, intelligent spaceships (like the miles-long Nostalgia For Infinity, partially taken over by a virus that feeds on computers), ancient alien races, and all the necessary technology to make these believable. In the hands of a better writer, the components - the content - of this book would be downright incredible.
However, Reynolds is not a good writer. His characters exist merely to move the story forward. I don't think any of the main three could seriously be called "heroes". It doesn't matter to me that they're all working against each other at certain times, but none of them ever seems real enough. Sylveste is a slightly egomaniacal scientist obsessed with uncovering the mystery of the disappearance of a race of aliens thousands of years ago. Ana Khouri is a mercenary hired by a mysterious stranger to kill Sylveste. Volyova is the commander (sort of) of a giant starship (mentioned above) that is also searching for Sylveste, because she needs his help. Beyond that, they are interchangeable. Only their motivations differ - they speak in the exact same voice, and their actions are hardly distinctive. You wouldn't recognize these characters if you happened to meet them anywhere else; they're just plot devices, and that is incredibly irritating.
The book takes about 200 pages too much in getting its plot worked out. It's very long, and I'm not sure how much of that length is really essential to the whole. Reynolds spends a lot of time with flashbacks - not important ones, just brief ones to tell you what a character was doing ten minutes before he/she was doing something else. Utterly superfluous. Another problem is his consistent use of passive sentences - even when there was intense action going on, it didn't feel intense. Instead of writing "Khouri walked down the hall", Reynolds writes "Khouri WAS walking down the hall." The overuse of the passive voice robs the story of immediacy and action.
Overall, I enjoyed this book, though on an entirely conceptual level. It was a painful chore to read (you have to make it to the last few pages before he explains the specifics of his plot), and I don't think I'll bother with the sequels.