Century Rain by Alastair Reynolds

I've enjoyed everything I've read by Alastair Reynolds so far (a novella, a few novels and short stories) but his 2004 novel Century Rain is not only the best I've read from him, it's the most enjoyable sci-fi I've read in a while.

Earth has been uninhabitable since the Nanocaust, but field archaeologists like Verity Auger still make trips there to study its artefacts. When she messes up on one of those trips, Verity is handed an offer she can't refuse and finds herself on a secret mission for which her expertise on twentieth-century Paris will be invaluable. Government scientists have discovered an unstable entrance to a poorly-understood galactic transit system whose origins they know nothing about. This particular branch appears to lead to nineteen-fifties Paris, though not quite the same version Verity's studied. All she has to do is use the transit system and retrieve the belongings of a murdered government agent who went through before her.

Meanwhile jazz-loving Paris-based private detective Wendell Floyd is on his uppers as usual, and takes on a murder case against his better judgement. At least, the client thinks it's murder but Floyd's inclined to go along with popular opinion and stick to accident or suicide. Until he starts to wonder if the victim was actually a spy, particularly when another one shows up.

This is part spy thriller, part space opera, part beautifully-rendered fifties noir, and I loved every minute. With more twists than a journey through an unstable pseudo-wormhole, Century Rain has tension, romance, dry humour, and a suitably tear-jerking Casablanca reference or two. It touches on ethics and the unknown consequences of new technology, but it can be approached simply as a wild adventure. I can particularly recommend it if you're a sci-fi fan who likes Raymond Chandler or Maigret, and if you've read and enjoyed Red Planet Blues by Robert J Sawyer you'll probably love this.