The new University of Michigan Press book Legal Stories: Narrative-Based Property Development in the Modern Copyright Era has a chapter on Lovecraft’s works and copyright. “From Yog-Sothery to Property: H.P. Lovecraft and the Making of the Cthulhu Mythos”. The author appears to be a comics copyright specialist, and the chapter is of substantial length (pages 74-122). Due at the end of July 2024, but Google Books already has a preview of some of the interior pages.