The best comic book art is usually found on the covers. That's because an artist can spend more time on a cover illustration than on any one of all the panels required for inside illustration. Oh, and the publisher always wants a flash cover that will generate sales, so that adds to the motivation.
An illustrator whose career has focused on cover art is Adam Hughes (born 1967). His Wikipedia entry is here, his web site here and he also has posted work and comments here.
The image above is the cover of his book dealing with cover work done for DC over the last 20 years along with other items. It seems to be doing well because the copy I recently bought is from the fourth printing.
Allow me to confess that I don't follow the comic book trade nor that of the graphic novels field. It's all so complicated these days what with editors and writers valiantly trying to keep their products fresh by reinventing backstories, creating alternative universes, assembling new character juxtapositions and diving headlong into politically correct themes. When I was a kid reading comic books, the superheroes simply went about their business of dealing with criminals of various sorts.
Another change from the good old days -- one that I approve of -- is the improved quality of cover art. Nowadays there is a body of illustrators who create dramatic scenes whose impact is heightened by the sound drawing and anatomical knowledge of the artist. Such illustrations and their creators are so prized that collections of their work are published in book form, as is the case for Hughes.
But Adam Hughes differs from the rest of that pack: he includes humor and a general light touch as opposed to depicting stern scenes of superheros in conflict with their opposition. Examples are shown below.
I wish I knew more about Hughes' background. He was born and raised in New Jersey but spent most of his career in Atlanta. He has called himself a high school dropout and on another occasion claimed that he didn't go to college because he was, as he has put it, too middle class to get financial aid and didn't muster the grades and test scores to earn a scholarship. As for art, he is essentially self-taught, which is probably a good thing; the usual art school training would have wasted a lot of his time.
That said, Hughes comes off as a sharp cookie in the commentaries he likes to make on many of his works. He knows art history and color theory plus a good deal of general history and other useful knowledge. I didn't catch any serious errors while reading through those commentaries. And by the way, those commentaries are salted with humorous bits; buy the book and enjoy!
This shows stages of Catwoman's head as it appears on the book cover. The image to the left is in ink and colored markers. It was scanned into Photoshop where coloring, shading and other details were added; this is Hughes' typical approach, though his convention demonstrations go no further than the ink and marker stage.
This isn't Catwoman, but instead her apprentice Holly who's recuperating at a diner after a rough night learning the cat burglar trade.
The Power Girl character is mega-stacked, and Hughes had some fun with it here.
Hughes is a big Art Nouveau fan and likes to use that style when he can get away with it. That's Wonder Woman, by the way.
Besides Catwoman, Hughes did a lot of Wonder Woman covers. He likes this illustration a lot because Wonder Woman is relaxed and smiling, which he feels is her true character.