The first graphic novel is said to have been written/drawn in 1978 by Will Eisner, creator of the famous work The Spirit. It was called A Contract with God and included four short stories. In the 80s, there were several landmark graphic novels such as Alan Moore's Watchmen and Art Spiegelman’s Maus, that helped cement the idea of a more serious comic book in people's mind. In the nineties, graphics novels grew by leaps and bounds, helped by such work as Cruse's Stuck Rubber Baby , The Hernandez Brother's Love and Rockets (this one started in the 80s) , From Hell by Eddie Campbell and Alan Moore, and especially by Neil Gaiman's Sandman, a perpetual favorite at book stores everywhere.
This is not to say that graphic novels were not often locked away in the sci fi/fantasy ghetto with a few seminal works poking out between broken spined editions of Dazzler, but the mere presence of them in bookstores helped put comics more in a mainstream context. To buy a pamphlet comic, you have to go to a special store which may or may not be filthy and poorly lighted and give up $3 for 25 pages of reading material. To buy a graphic novel, you go into a bookstore where lots of normal people go, and get an object that could be reasonably passed off as a normal book in case your significant other comes over. You also get lots of comics at once instead of having to come back month after month.
Graphic novels also helped the diversity of the comics medium. For July 9th, 2002, Amazon.com's top selling graphic novels are Watchmen, Murder Mysteries (Neil Gaiman is writing), Sandman Book #1, Tim Burton's Melancholy Death of Oyster Boy, Jhonen Vasquez's (creator of Johnny the Homicidal Maniac) Squee's Wonderful Big Giant Book of Unspeakable Horrors, Origin, From Hell, Daredevil: Born Again, Ghost World, Harlequin Valentine (another one by Gaiman!), V for Vendetta, Blade of the Immortal: Secrets, The Dark Knight Strikes Again Book 3(by Frank Miller) , Akira vol 6, Sandman Book #3, Johnny The Homicidal Maniac : Director's Cut, Sandman Book 2, Essential Spiderman #2, Jimmy Corrigan, To Afghanistan and Back: A Graphic Travelogue , Daredevil: Yellow, Sandman #4, Kingdom Come, Akira book #5 and Essential Spiderman #3.
This list has horror, slice of life, action, manga, fantasy, even non fiction. Sure, we have some superheroes in here, but this is a more robust list than you would get from seeing the top 25 sellers at a store with ten copies of each of the ten X books. Compare to July's top 25 comics (http://www.icv2.com/articles/news/1555.html) For GNs we have 16 or so non superheroes, and for comics we have 4 (and those are two Transformers books, Battle of the Planets, and G.I Joe) That's 64% non super hero vs 16%. This is not to put down super heroes, people will always desire the fantasy of good triumphing over evil, but as someone once said, it wouldn't be much fun if 90% of all books were nurse novels.
I believe that the difference in genre diversity may be due to different demographics. There is anecdotal evidence that Sandman is popular among women, and the kid you see reading Spiderman is certainly different from the kid you see reading Johnny The Homicidal Maniac. I'm not saying that there aren't any Spiderman graphic novels, there certainly are. What I'm trying to say is that a graphic novel encourages a new type of comics fan: The comics reader.
The comics reader buys comics because he/she wants to read comics. They don't buy them out of habit, nostalgia or because Caped Avenger #4567777 is going to be worth a million dollars one day. They buy them because they want to see what someone can do with some paper and ink and word balloons and panels. They want Spidey to sling some webs and save the day, they want to see if Irving Flavour will win out against Zoom comics, they want to know if the snow will be ice or ash.
Personally, I read graphic novels because I don't want a tiny little bit of a comic doled out like there is some comic Nazi out there saying "Only 22 pages of Spider-man for you this month". No, I want huge chunks of comics, I want to take that comic home and revel in comics for hours. I want that complete story sledgehammering me in the chest. I don't want to wonder what happens next month. I want to be thinking about the end of the story. I want to be thinking is that the end for those characters I laughed with and cried with and who kept me up at night?
The best part of many graphic novels is that there is an end. The problem with those immortal monthly superheroes is the same with the sitcom of yore. Yea, you can try for that emotion, but in the end everything has to be reset back to the status quo. Sure, Robin might die in the next issue of Batman, but we all all know he is going to be resurrected. But in a graphic world, Speedy might die, and you're going to cry, because he's not coming back. A series can be brought to a graceful and dignified end instead of lingering on forever. Graphic novels sell differently than regular comics. The regular comics market is obsessed with new new new, if an issue is a week old, it might be too old, put it down cold in the back issue bin. However, Watchmen, the number one item on the best seller list is from 1986. Graphic novels sell in perpetuity.
Half a comic's value is in its newness or its oldness its rarity or lack thereof. But what a graphic novel has to offer is between the covers for a bargain price. So everytime a new person hears of a series, they don't dig through bins for messy comics to put in mylar bags and shove in long boxes, they get the first graphic novel. However, the difference between graphic novels and singles has caused a few problems for the comics business. Most comics publishers use single sales to see if a trade would be good, but for many mature title, there is the phenomena of waiting for the trade.
It makes sense, why spend time picking up books one by one, when wait a few months and you get them cheaper and all at once? Maybe the comics industry needs to change on this point if they want to become more mainstream. After all, the American comic book came from the comic strip, which used to be a much more impressive animal. The Spirit was once given an entire page, and now comic strips are lucky to be readable by the time the shrinkage is over.
Maybe graphic novels are a new step forward for comics, or maybe they are just a red herring, but I know that they are changing the way I read comics.