What is the name of the book about a man who gets lost in space and goes crazy?

[sweetestkiss]

I don't know the details of this book but it's about a man who somehow gets lost in space and there is no way to get back home. Also he can't die, I don't know why. So he's out there for hundreds of years and he goes crazy, but so many years pass that he turns sane again. I heard about this book from a friend who forgot what it was called. Does anyone know?