This would have been an Ace double, if it hadn't been published by Belmont/Tower. But the bundling of Harlan Ellison's "Doomsman" with Lin Carter's "The Thief of Thoth", does present linked themes, and common experiences for the reader. I can see the principal characters being conflated, and the whole thing turning into a TV series that would have had three seasons on the "Space" channel. and it would have been good, clean amoral post-apocalyptic fun. the Novellas are exactly that.
There's no ISBN, and not even page numbers in this very cheaply bound and printed book. WAs this some kind of rip-off? I don't know. ( )