I admit, it's one of the books I have in battered paperback for carrying around, and also in nice hardcover for keeping over the long haul. I don't double up that often, but...sometimes you just gotta.
.
Me too, but my hardback is signed by both authors.
It stays in a nice safe place for occasional looks, while the poor, battered paper back takes most of the abuse of being re-read.

Mine too but I've lent it out to someone. I want it back now. Not because I think she'll lose it (she won't) but because now I want to re-read it and it is my only copy.