In a (well-worth checking out) interview at New Statesmen, Grant Morrison talks about why he’s leaving superheroes for awhile:
I knew I was coming to the end of Action Comics in [issue] 16, I knew I was coming to the end of Batman in issue 12, of Batman Incorporated, and it just seemed like I had all this other stuff building up that was completely different from that, and it seemed like a really good time to stop doing the monthly superhero books. And also having to work with so many artists on Action Comics, it’s not that the artists are bad but I’m sometimes working for three or four guys at a time, which means you’re writing issue 14 before you’ve written issue 12 and then you’re sending in six pages of issue 13 to someone else. So it was just too hectic. I just didn’t want to do it any more.