It's Comic Book Day. Yeah, I didn't know about it either, but it's here, nevertheless. (Not to be confused with Free Comic Book Day, which was in May. Sorry.)
At Pajama Guy we've debated the worth of comic books. Are they a true art form? A useful stepping stone to real literature? Or just cheap enjoyment for the semi-literate? If that last characterization seems harsh, remember the scare in the 1950s when parents across the nation worried that comic books were leading to the destruction of American youth. That's why the Comics Code Authority was imposed in 1954, and kids have been well-mannered ever since.
Understanding Comics: The Invisible Art, by Scott McCloud. Published in 1993--as a comic book, of course--it shows the grammar of comics, and explains what they can do, looking into the past but also toward the future.
The book notes that comics engage us in a special way, since we the reader finish the comic, as it were, by filling in the gaps between its panels. And McCloud himself is the narrator, appearing to us, explaining things to us, moving the story along in which he is a character.
He followed this book with Reinventing Comics in 2000 and Making Comics in 2006. Both worth checking out, but Understanding Comics is the essential one.