In noting that a proposed comics adaptation of Burrough’s PRINCESS OF MARS appears to have been taken behind the stables and shot, Heidi Mac makes an aside I was unaware of. Apparently, that book is public domain.
However, the other books in the sequence clearly aren’t. And Heidi suggests that trademarks may also apply.
Is this a case where a work being public domain essentially means nothing at all? Does anyone with expertise in the field actually know?
(That’s as opposed to, “I know absolutely nothing about any of this, but my opinion is…”)