I was happy to see Alastair Reynolds setting a novel in a different universe than his first several books, good those those were. And I was interested to see if his particular talents survived transition to a different setting.
In Century Rain, I can say unreservedly that his spectacular hard-SF imagination is as evident as in his earlier books. That said, some of Reynolds's weaknesses remain: this book is as long as the earlier ones, and I rather think each of his novels would have been better at 3/4 the length or less. His prose is serviceable but not really elegant. His characters (with a couple of exceptions) are fairly stock. But that is -- well, not quibbling, but acknowledging weaknesses that are not fatal weaknesses. So -- acknowledging its weaknesses, I still enjoyed this novel, and I was often fascinated, by the end quite moved, and occasionally awed.
The story begins on two threads. One concerns Wendell Floyd, an American in Paris in 1959. But his Paris is rather altered: its technology lags our own 1959 just a bit, apparently because World War II never happened: the German advance on France stalled in the Ardennes, and Hitler was shortly later deposed. But the evils of fascism were not eliminated, and France in 1959 seems ready to come under the sway of a nasty nativist politician. Floyd is a sometime jazz musician who mainly works as a private detective, and he is drawn into investigating the mysterious death of an American woman, a death the police seem only too quick to write off as an accident or suicide.
Meanwhile, three centuries in the future -- our actual future, it seems -- Verity Auger is an expert on Paris in the "Void Century": the 21st Century. It seems that late in this century something called the Nanocaust wiped out life on Earth. Humans survived in orbit, and have split into two groups: the Threshers (including Verity) oppose almost all nanotech and bodily modification, while the Slashers embrace it. The two are close to fighting a war over possession of Earth. Then Verity is maneuvered into accepting a strange assignment: wormhole travel back to Paris in 1959. It seems another Thresher agent has just been murdered, and Verity must try to recover some valuable information she had gathered.
Obviously, the Earth to which Verity is traveling is Wendell Floyd's Earth, and the murdered Thresher agent is the woman whose death Floyd is investigating. Wendell and Verity cross paths, and sparks fly, as we might (being experienced readers) expect. Their romance is a bit underplayed, and not quite convincing. But they also uncover a series of mysteries, involving the Thresher/Slasher war, factions among the Slashers, and some really bad guys, including some nasty apparent children. And they learn the true nature of Floyd's alternate Earth (which reminded me oddly of Robert Charles Wilson's Spin). The resolution of these SFnal ideas is pretty cool for the most part. The driving motivations of the bad guys, however, are never quite real -- they are just a bit too genocidal for no terribly good reason. But the story does come to a satisfyingly exciting close, and Floyd and Auger's personal story is well resolved as well. It's a good book, not a great one, but certainly it serves notice that Reynolds remains a writer to watch.