I almost miss this book because of mixed reviews here and there. I would have been wrong. It's all good, just a little bit heavy in some passages, but everything fits, and we pay for: was the solar sail, the virtual world, nanotechnology, artificial intelligence, alien artifacts, aliens, credible protagonists, controlled narrative. Stross rises here at a Vernor Vinge, Neal Stephenson and Greg Egan. Do not miss.