The Lurker at the Threshold

Blurb

The Lurker at the Threshold is a short novel in the Cthulhu Mythos genre of horror. It was written by August Derleth, based on short fragments written by H. P. Lovecraft, who died in 1937, and published as a collaboration between the two authors. According to S. T. Joshi, of the novel's 50,000 words, 1,200 were written by Lovecraft.
The novel was originally published in 1945 by Arkham House in a hardcover edition of 3,041 copies, listed as the second volume in the "Library of Arkham House Novels of Fantasy and Terror". A British hardcover followed from Museum Press in 1948. The first British paperback was issued in 1970, with an American paperback published by Beagle Books in 1971. The novel has since been regularly reissued by Ballantine Books, then by Carroll & Graf. A French translation, Le rôdeur devant le seuil, appeared in 1973.
Lurker was included in The Watchers Out of Time and Others, the 1974 Arkham House omnibus edition of Derleth's stories credited as collaborations with Lovecraft.