I find it hard to believe that my son only got interested in graphic novels in December 2010. It seems like we've been sharing books for ages. The book that first piqued his interest was Copper by Kazu Kibuishi.
Copper is really more of a comic book anthology than a graphic novel but there is some on going character development. Copper and Fred, a boy and a dog who share adventures that span the mundane to the fantastic.
Copper has dreams of things as well that sometimes bleed into reality and sometimes it's difficult to tell if he's awake or a sleep. Some stories are self contained and others span six or so pages.
For me, I wanted more cohesion and more plot. My son, though, who was new to the format loved having everything so short and straight forward.