Back in the day I used to read Terry Pratchett's Discworld series of fantasy novels. They are totally awesome, but what first drew me in as a kid were the mind-blowing covers Josh Kirby created for the books. Check out his website here
"Ronald William "Josh" Kirby (27 November 1928 – 23 October 2001) was an English commercial artist born in Waterloo, on the outskirts of Liverpool, Merseyside.
Kirby painted film-posters, magazine and book covers. Creating a total of over 400 cover paintings, his personal preference was for science fiction jackets and his work on the covers of Terry Pratchett's Discworld series of novels is well known. He also created the poster art for Monty Python's Life of Brian and Star Wars Episode VI: Return of the Jedi. He worked almost exclusively in oils. Charles de Lint said Kirby stood apart from most genre commercial artists for 'his own flair and unique vision'" (Wikipedia article)