It’s called Sam & Max: Surfin’ the Highway by Steve Purcell. It’s also, unfortunately, out of print. You may be able to find a used copy through amazon or ebay. Don’t know if I’d recommend it to anyone with abdominal surgery, through, because I can’t read it without cracking up.
My first and best recommendation would be Hellboy by Mike Mignola. Once again, Hellboy. My favorite comic series ever: astonishingly beautiful art, very subtly-told stories that perfectly combine humor, action, and horror, and it sounds like it fits in with your interests. There are several trade paperbacks; Seed of Destruction is the first, and The Chained Coffin and Others is my favorite. The only reservation I have is that they’re heavier on mood than on dialog and plot, so I don’t know if they are good time-killers.
The best graphic novel I ever read was Batman: Year One by Frank Miller. I don’t really like any of Miller’s other stuff, and I’m not a huge fan of Batman; I just like well-told stories.
From the OP it sounds like you’re much more familiar with manga than I am, so these might be old hat: Lone Wolf and Cub is huge and very well-done; I imagine you’d be fully recovered by the time you got halfway through that series. A second for Metropolis. And if you don’t already have it, have you considered a subscription to Shonen Jump? The English-language version started fairly recently, and while I feel a little bit guilty reading stuff that’s so clearly directed towards children, I have to admit that it’s fun having a steady supply of something that big and that easy & fun to read.
Lynn Bodoni already mentioned Terry Pratchett, so I’ll second the Discworld books. Especially if you’ve read Good Omens. Because Good Omens is one of my favorite books ever, I’d tried reading some of the Discworld books before. But they always seemed light and never held my interest. Recently, because Pratchett gets so much good press on this message board, I picked up a couple and now I’m hooked. I feel okay suggesting them in a graphic novel thread, because they read somewhat like graphic novels – they’re not stupid, but they’re easy to read, and are carried mostly on the level of imagination in them. Vampires, werewolves, wizards, dragons, time travel, all thrown together in the same story like the best comic books. I started this round with Night Watch and loved it.
In the same vein, Dirk Gently’s Holistic Detective Agency and The Long Dark Teatime of the Soul by Douglas Adams are great, fun books to read.
Good luck and hope you have a speedy recovery, meenie. Enjoy the chance to read.