Some people, like Laurens Bancroft, have lived for hundreds of years and are the rich elite called Meths (after Methuselah). When he is murdered before he is able to back up his consciousness, his next clone, with the vital block of data missing between back ups, employs Takeshi Kovacs, the last Envoy soldier, to investigate his murder.
Essentially it is this premise that makes the book an interesting read above a science fiction detective novel. The murdered can be brought back to see justice is done by identifying their killer. Criminals can be downloaded into the mainframe and kept on ice for years whilst others inhabit the body. People become reckless and regard their bodies as just worthless shells they can use and abuse.
