My first thought is any Peanuts or Calvin and Hobbes collections. My kids pour over these constantly. They're good for short attention spans, since you can stop after any strip.
If you're looking for high school level reading, let me know, and I'll revise this list.
Monthlies I'd look at:
I haven't read them, but I've seen some pages of the art, but the original Dragonlance series is currently being adapted to comics. If he likes LotR, he might like that too.
Impulse is basically "Kid Flash." He's supposed to be 14, but he's short of attention and hyperactive, which results in amusing circumstances since he has superspeed. He's a character I think a young person can really enjoy reading. Most of the other "teen" titles by DC and Marvel (or Image or Darkhorse) are not ones I'd recommend for younger persons, since the themes of most of the arcs for Superboy, Robin, and Supergirl are all decidedly adult most of the time.
There was a new title out by an independent press that I really enjoyed. But I can't remember what it was. I'll have a looksee for it next time I'm at the shop (soon). It was about a child whose parents divorced and then moved with her mother to a small town. It looks at her adventures there with her new friends (one of which may, or may not, be a superhero).
DC does a line of comics based on Cartoon Network properties: Krypto (Superman's dog), Scooby-Doo, et al. These are amusing but not fantastic books. They are, perhaps, too simplistic, but if you have a child who is really stubborn about reading, it may be what you need.
In addition, the "adventures" series are targeted toward a younger audience and feature all the standard DC universe characters (batman, wonder woman, superman, et al).
Graphic Novels:
Leave it to Chance is about Chance Falconer, the 10-12 yo daughter of Lucas Falconer, the mystic protector of Devil's Echo from the likes of the ghosts, zombies, vampires, werewolves, and the like. Also, she has a pet dragon.
While the "Devil's Echo" makes it seem a bit creepy, and it is about horror movie stuff, I seriously haven't found anything that children would object too. And it's not pushing any agendas. The Falconers are more or less the unquestioned good guys. THere's no reason to think they're anything but good guys, and the closest they've come to breaching any religious issues is including a Native American medicine man in one story. They try very hard to make it child friendly. Â I recommend it because it's about a kid, but it doesn't talk down to them while maintaining a simplicity that kids can keep track of. Of course, I have daughters, so the idea of a girl protagonist doesn't worry me, not sure if your son thinks girls have cooties or not though. This is actually one of my personal favorites
There are also some collection of the old Superboy comics. These featured Superman as a child in Smallville (when they were written, it was assumed he always had his superpowers). The scripts were simple and another child protagonist helps kids get into it.
Usagi Yojimbo isn't one I'd normally recommend for children, since it's so... literate. But it's fantasy/historical fiction set in Medieval Japan -- with anthropomorphic animals for characters. Usagi himself is a samurai ronin. He frequently is accomanied by a rhino bounty hunter. He does a lot of work for Lord Noriyuki who is a panda. Child characters show up, but the story isn't intended for children. I bring it up because you say he likes/can follow LotR.
Superman for All Seasons is essentially an overview of Superman's life, it looks a little at him growing up, a little as his freshman year in Metropolis, and the development of his relationship with the people in Smallville and Metropolis and his arch-nemesis. Less action than a typical Superman intro story, but a good look at him as a character.
I'm sure I'll think of some more soon. With all of them, of course you'll want to at least look through them before handing them to the kids.
