August Derleth is perhaps best known as the man who kept H. P. Lovecraft's work alive after that author's death in 1937. As a friend and correspondent to Lovecraft, Derleth and fellow fan donald Wandrei tried to get publishing houses interested in publishing a collection of Lovecraft's stories; getting no interest, they founded the small press Arkham House to keep Lovecraft's name alive. Soon, the legendary publishing firm was run by Derleth alone, introducing a host of fantasy and horror authors who might otherwise have fallen into the literary cracks of history.
Derleth had access to Lovecraft's commonplace book and used scraps from it to produce "original" stories by Lovecraft in collaboration with himself. He also codified Lovecraft's "Cthulhu cycle," twisting it in ways that Lovecraft had perhaps never intended. Many Lovecraft fans now disdain Derleth because of this but, without Derleth, Lovecraft would most likely be a forgotten writer today.
Derleth, as a writer and editor, had many other arrows in his quiver. He was one of the country's leading regional writers, something which is talked about briefly in the interview below. He was a regional historian, a fairly distinguished poet, a literary critic and teacher, biographer, mystery writer and creator of the popular Holmesian character Solar Pons, and author of the juvenile (because the young adult category had not yet been established) series about The Mill Creek Irregulars. It is fair to say, however that without his work promoting Lovecraft and (through Arkham House) other important fantasy writers, most ewould not be aware of Derleth.
The interview below, from Robin Laws' Black Clock Audio Tales Special #15 podcast, is with Kenneth Hite, a role playing game designer, writer, and expert on Lovecraft. Be aware that this podcast is not the most focused you might encounter. It rambles and, at times, denigrates Derleth (something that I, a devout reader of over 100 books by Derleth, find a bit off-putting), and does provide some necessary context. Nevertheless, there is some good information about Derleth and his importance in the field of the weird tale.
With that caveat, let's go to the podcast: