My review from Amazon.com:

Incredibly ambitious, but it works
Publishing’s a funny old business. Reynolds’ magnum opus, “House of Suns” has only just come out in hardback in both the UK and the US, but I found a paperback copy at Singapore Airport last Saturday. I hesitated for a moment – this is a big book: did I really want to lug it around the world? – but only for a moment.
One of the age old problems in science fiction is that of the speed of light. How can one write a decent space opera, with exotic starships visiting improbable planets, without violating the speed limit? Reynolds decides to stick with relativistic limitations (well, mostly) by playing with the other side of the equation: time. The result is an extraordinary mystery story at galactic scale, in which (for a few travellers) time is measured in thousands, even millions of years.
“House of Suns” is an audacious work. I’ve enjoyed all of Reynolds’ earlier books: even though the stories were more conventional than, say, those of Iain M. Banks, Reynolds confident mastery of his material has been undeniable. In the new book, he takes quite a few risks, and gets away with them. The conclusion… well, my first reaction was confusion, but I found myself realizing how utterly apposite it was.
Comparison between writers is invidious, but inevitable. Right now, two of the best science fiction writers are British: Banks and Reynolds. Before “House of Suns”, I would have said that Banks was clearly the greater talent. Now, I’m not so sure. What fun!