The Ophiuchi Hotline, by John Varley

One of the things I enjoy best about reading Speculative fiction is the fact that more often than other most other genres it leads to these great moments for me wherein I have to take another look at my own world and try to view it from another perspective.

John Varley's The Ophiuchi Hotline largely asks the question, "What makes me, me?" The main character, Lilo begins the book waiting for her own execution for genetically modifying human DNA, then she is offered a bizarre choice; a clone of her is brought in and offered to be killed in her place, if she agrees to take on certain work in secrecy for the government. Then the clone, coming to full awareness, states that it will happily do this job if the agent chooses her over the original...

The next chapter (2) begins with one of the Lilos killing herself before execution and the other beginning the new work, but specifically doesn't inform the reader who we are now following - over the course of the novel more than a few additional Lilos begin to pop up (sorry for the mild 38-year-old spoiler), and again and again the reader must decide which, if any, of these protagonists have more validity than the others.

The story travels throughout our solar system, involves aliens and alien invasions, but focuses largely on the morality of cloning and the question of identity.

A truly fascinating read.