The long form comic is where we run into a bit of confusion and my slight annoyance. Technically, a graphic novel is a comic story written and published in a long form. Companies also, however, bind together several issues of the shorter form "comic books" into a long form book and publish that as what is known as a trade paperback.
My annoyance is simply this, I feel like the term "graphic novel" has been appropriated by mainstream folks to represent "serious" comics which are suitable for adults to read. It's used as a term to justify participation in an activity and a medium which those people still deride as beneath them by removing any mention of "comics" from the name. This becomes all the more apparent when you consider that all of Alan Moore's major works, including the much vaunted V For Vendetta and Watchmen, were originally published as individual comic book issues. Preacher, soon to be made into an HBO Original Series, was published as comic books. I don't call Faulkner's stuff literature in fear that people will think I read Danielle Steel if I call them books.
Now, I said this was a minor annoyance and that's true. A world where people are discovering that comics are more than men-in-tights is better than a world where that 's not happening, even if they're being coy about it through the clever use of labels. There is a useful place in our terminology for graphic novel, but let's agree not to use it as a code word for "cool" or "serious".
Update: Here's an excerpt from Roeper's review of 300 that's exactly what I'm talking about.
"If you thought "Gladiator" was a bit too stingy with the bloodshed, if you
felt "Sin City" could have been more stylized, if you hate it when the masses
refer to graphic novels as "comic books," this is your day.
For today brings about the release of "300," and it is the "Citizen Kane"
of cinematic graphic novels."