Humans have received a message from aliens, and sent a reply. Sarah, the scientist responsible for decoding the first message, has lived a long life. When she's eighty-seven years old she learns that a second message has arrived. The new message is encrypted in a way that no one can understand, so an extremely wealthy man asks Sarah to get involved in the decryption effort, and offers her an expensive "rollback" that will return her to youth. She insists upon getting a rollback for her husband, Don, as well. Then Don's youthening process works, and Sarah's doesn't, so he returns to being physically twenty-five or so, while she remains eighty-seven.
Cool premise. The development of the story from there was good--I mean, this is Robert Sawyer, after all--but it turned into the story of how poor Don struggles to cope with suddenly being physically young again, and I couldn't quite buy it. I could believe in his disappointment about the failure of Sarah's rejuvenation, but his existential angst about what he might do with himself for an extra several decades just didn't crank my sympathy. I was more interested in the content of the second alien message and what came out of it, but that was wrapped up quickly at the end of the book.
The science fiction element was there in the novel, but I think that people who usually read mainstream fiction might like it better than a dedicated science fiction reader, because ultimately the story was more about relationships--with a side of scientific speculation--than about big new ideas.