This is a real page turner with just enough science and just enough fiction. Set in a world where several series of clones are dispatched into the galaxy to observe the rise and fall of cultures. They have periodic reunions and literally swap memories, creating a long timeline of visits to civilizations and observations of wars and changes in the galaxy. Though the two main characters could have used a little more development, the story line kept me interested. Ending was a bit unsatisfying, but a good book overall!