Who Goes Here?

Description for WHO GOES HERE?  by Bob Shaw:

Shot at by aliens, eaten up by monsters, frozen up, burned up and shipped all over the galaxy¿ war was one game Private Peace didn't want to play. So why had he joined the Space Legion?
Warren Peace had joined the Space Legion to forget - exactly what, he hadn't the faintest idea. But he was sure about one thing - however horrific the crime he'd once committed, the memory of it could hardly be more unbearable than life in the lunatic Space Legion. Private Peace knew he'd got to get out¿
The trouble was, the only way to escape his 30-year contract was to discover exactly why he'd signed it in the first place. And that meant a hair raising journey into his forgotten past to meet the one person Peace definitely didn't want to know - Warren Peace Mark I - in other words, himself!