Edward Gorey was a remarkable illustrator with a quirky and subtly-demented sense of style. Probably his best-known work is the animated introduction to the PBS series Mystery, but he's done a number book covers and such, as well as several books of his own -- including children's books that would probably give the average little child nightmares. He died on April 15, 2000.
For a FAQ and bibliography of his works, check out The Edward Gorey Bibliography Web Page.
Also look at A Tribute to E. Gorey and Goreyography.