One of the great qualities of Shadow World as a game setting is the number of different “styles” that can be found in the various books. No matter what type of fantasy game you play, you can probably find a place or time in Kulthea that can work for you.
Cross-genre. SW’s sci-fi elements and tie in with Spacemaster were pretty novel for a fantasy setting in the late 80’s. For GM’s that like the “ancient astronaut” angle or want to run a Gene Wolfe style campaign, SW has a great back story and cool tech that co-exist with the more traditional fantasy elements.