Been reading it lately, and it helps reduce my scrolling time. I've hardly read any, so you can recommend really popular stuff, too.
I've read Vagabond, 20th Century Boys, Claymore (years ago), and some berserk. I just finished reading Teppu, which I thought was an interesting subversion of a lot of anime tropes. I also liked that it was a short run (only 8 volumes). I guess I like seinen, but I've also enjoyed josei like She Loves to Cook, and She Loves to Eat.
Anyway, no shonen please. Hard mode: please nothing about high school
The movie covers a third of the actual story. It was made while the Manga was being published, so it left a ton out out of necessity. The biker gangs are more fleshed out, and there's a good amount of post apocalypse story telling. It is long as hell (2000+ pages), but there's still nothing like it.
Still worth noting that the movie was also done by the mangaka as well, so the Movie is more like an Alternative ending, that is technically canon in its own way.