Under their Black Wings has a useful overview review of Discovering H.P. Lovecraft, edited by Darrell Schweitzer, with a focus on “The Derleth Mythos” by Richard L. Tierney.

For those looking for a paper copy I’d add that you should know that there was a “revised and expanded” edition in 2001, so be sure not to get the earlier edition from eBay. Also that the revised edition is now in a budget £3.80 Kindle ebook.