I'm trying to find the name of a book I read awhile ago. It involved a bunch of gateways that you could sort of fax yourself to. You could have multiple copies of yourself running around and if one of them died they could be recreated from the last time they went through the portal. The story is about someone going around and killing all the copies of this guy, I also remember a part where he found copies of himself and of his attempted murderer that that guy had tortured almost beyond recognition.
Anyone know this book?