My own experience with them in a school library has been very positive. For whatever reason there are students who can read the words in a story but do not see the "movie" playing in their imagination. Comic books bridge that gap in the ability of a reader to call the words and see the story the words are painting. The challenge for librarians is finding materials that fit into the age level of their students.
I attribute my own love of reading to Nancy Drew mysteries and the comic books that my mother purchased for us from a news stand that sold English language materials when we lived overseas.
USAToday has a terrific article on the subject today. The article focuses on Jeff Smith author of the Bone series. He remembers being overwhelmed by the enthusiastic reception he received from an ALA meeting.
The article quotes Jack Gantos (author of Rotten Ralph, Joey Pigza and the Jack Henry books) on the subject.
Jack Gantos, author of the popular Joey Pigza series of children's books, says adults should be delighted by kids' attraction to comic books - or any other lightweight material - if they want them to read heavier books down the road. "Kids have beach reading just like adults have beach reading," he says.
Even French philosopher Jean-Paul Sartre loved comic books, Gantos says. "This is a pretty heavy thinker, but he said in his autobiography that he started off reading comic books as a child and that if it wasn't for comic books, he never would have stuck with books.
"That was really where (Sartre) sort of punctured the world of literature and really got excited about books," Gantos says.
This is an excellent article, you should read the whole thing.