Egads... I didn't even hear about this one... he released some books which were on the shelves for a few minutes about 10 years ago, but otherwise he was a difficult find...
When I heard I rented every callahan book I had at the library. His one panel style is what got me into comics in the first place along with Gary Larson. Its depressing enough to turn me into a raging alcoholic. Bob Schimmel too.