Discworld is a comedic fantasy book series by the British author Terry Pratchett, set on the Discworld, a flat world balanced on the backs of four elephants which, in turn, stand on the back of a giant turtle, Great A'Tuin. The books frequently parody, or at least take inspiration from, J. R. R. Tolkien, Robert E. Howard, H. P. Lovecraft and William Shakespeare, as well as mythology, folklore and fairy tales, often using them for satirical parallels with current cultural, political and scientific issues. Since the first novel, The Colour of Magic (1983), 37 Discworld novels have been published as of October 2009, four of which are marketed as children's or "young-adult" (YA) books. The original British editions of the first 26 novels, up to Thief of Time (2001), had distinctive cover art by Josh Kirby; the American editions, published by HarperCollins, used their own cover art. Since Kirby's death in October 2001, the covers have been designed byPaul Kidby. Recent British editions of Pratchett's older novels no longer reuse Kirby's art.