By 'explicitly Lovecraftian' I mean referring to characters and settings first mentioned in the works of H. P. Lovecraft. If my story is about the rise of Cthulhu from the dread city of R'lyeh, I'm very explicitly using characters and settings created by Lovecraft.
Your post raises two separate and distinct issues. First, referring to the above, you may be confusing "copyright" with "trademark". Copyright refers explicitly to textual material; trademark protection gets sought for the use of names and other similar material in the context of certain kinds of products or services. I don't know about Lovecraft, but I can provide a similar example from the same era:
Edgar Rice Burroughs became a HUGE success with the publication of
Tarzan of the Apes in 19xx. That success led him to write many sequels, rapidly, over the next few years. The original and a number of the sequels have lapsed into U.S. public domain, which means anybody can reprint them for publication, freely, without paying royalities or getting legal agreements.
HOWEVER, Burroughs obtained trademark protection for the characters (Tarzan etc.) and the setting of the stories, meaning you can't write a new Tarzan story without permission of the trademark holders, now the Burroughs estate. As I said, I don't know if this applies in any way to Lovecraft's milieu.
Yes, my understanding is works before 1922 are definitely in the public domain. But that doesn't mean everything written after that is still under copyright. Anything written between 1923 and 1963 was only under copyright for 28 years, then must have had the copyright renewed within a certain time frame. If it was not, it is in the public domain.
Mostly correct. Actually, in U.S. terms, public domain dates from before 1923. 1922 is fair game, generally.
More important, however is your correct understanding of the 28-year copyright protection term, which could be renewed for an additional 28 years, during the years you cite. Since then, the laws have changed, and never retroactively. Anything still under copyright in 1963 came under the protection of the terms of the revised law. That situation still applies.
And, in general, anything likely to have been considered a valuable copyright-protected property would have had the copyright term extended via the 28-year extension statute. Examples certainly would include the works of Faulkner and Hemingway and Steinbeck, all still protected by copyright to this very day. Among many others.
As I mentioned in an earlier post, the Lovecraft situation has been contentious, for a variety of reasons, not least including the efforts of Lovecraft's acolyte and would-be successor, August Derleth, to cash in on Lovecraft's mythos. I understand that he, and his Arkham House publishing business, have historically been very litigious in asserting copyright protection for Lovecraft's works.
caw