I've read most of Cerebus, which is saying a lot because it was a 300-issue series collected in phone book sized graphic novels. What I can say about it is that there are parts that are really enjoyable to read and parts that are confusing and clunky. Some of it made laugh a lot, mostly the High Society and Church & State arcs, and the Melmoth book is fantastic. The art is terrific, especially once Gerhard starts doing the backgrounds. But then there's the problems with the story. Dave Sim isn't a good writer. He does jokes and satire well, and his concepts for characters and theme are interesting, but when it comes to the actual composition of plot and script, he falls flat. He'll spend an entire 22-page issue dealing with an internal dialogue while the character sits in the chair...22 pages of this...and he will go on ad nauseum with a lot of confusing quasi-narrative while shooting through space for several chapters, all to set up the back story, but there are many points where huge events in the actual story are glanced over in a couple pages. He does that a lot, actually, and it gets confusing. I'm also of a mind that he changes his ideas of the direction of the story several times, changes the nature of a lot of characters more than once, and has a habit of stopping the story altogether for several chapters to tell some side story. This isn't to say that there isn't a lot to draw the reader, but his 300-issue story could have been a 200-issue story without losing much. Also, it's an anthropomorphic aardvark, the only anthropomorphic character in the story aside from two other aardvarks, and in the 200 chapters I read, there was never an explanation of why. That's not a big gripe, it's kind of whatever, but it's weird.
I don't recommend against reading Cerebus, but I never recommend that people do.