Imagine a more cyberpunk take on Trigun, with a less lighthearted protagonist, and you'd have something like Eat Man. There's a bit of a fantasy element at play here too, with monsters and kingdoms and such, but the overall sci-fi western flair reminiscent of Trigun takes center stage.
That said, the world doesn't exactly feel cohesive, with so many different elements at work. It doesn't help that the story is very episodic, with Bolt jumping from job to unconnected job with nearly every chapter. His adventures do tend to be a fun time at least--even though a couple of them end a bit abruptly. Just don't expect anything to get explained: from why there are dragons and ancient swords in the same setting as airships and cyborgs, to things as central as the question of why Bolt has the power to eat things, and regenerate them out of his hands.
So far, Eat Man is an entertaining bit of sci-fi action adventure, with nicely detailed old school art, and some nice vignettes. It's a quick read, and a decent palette cleanser if nothing else. I know there's at least one other volume, because I picked it up at the same time as this one, so maybe that'll fill in some of the gaps. But if it's just more fun, mindless adventure, that would probably be fine, too.