Apple has created a feature area for comics and graphic novels in the iTunes store.  The launch coincides with the addition of 80 Marvel graphic novels to the iBooks store, including Civil War, Castle, Dark Tower, and Avengers.
Marvel is also offerieng graphic novels on Barnes & Noble's Nook (see "Marvel Graphic Novels on Nook Tablet").
Other featured titles in the iTunes stores include The Walking Dead, Fairy Tales for Angry Little Girls, Harvey Pekar’s Cleveland, and comic strips such as Garfield, Dilbert, and Pearls Before Swine. 
The number of titles is limited, but the build-out of the section implies that Apple plans to grow the number of titles in the future.