What’s slipping into the public domain in the UK in January 2017? Of course H.G. Wells leads the public domain pack, in terms of science-fiction.
Others of note are:
* Otis Adelbert Kline who “contributed numerous stories to Weird Tales magazine”, wrote some pulp novels in the Edgar Rice Burroughs ‘planetary romance’ style, and who was later a literary agent for the great R. E. Howard.
* Lionel Atwill who was a horror and supernatural screenwriter for RKO, Fox and Universal, with films like Sherlock Holmes and the Secret Weapon and Frankenstein Meets the Wolf Man and House of Dracula.
* Walter S. Masterman, a British mystery novelist whose titles seem to put him on the ‘macabre’ shelf.
* Cyril G. Wates, who had a number of pulp stories in the science fiction pulp Amazing Stories in the late 1920s.
* Albert Leffingwell, an American author of quality mystery novels.
* Booth Tarkington, author of The Magnificent Ambersons and many others.
* Karl Hans Strobl, Austrian fantasy and horror writer. The English translations would, of course, not be going into the public domain. But the plots and approaches will be. Some of his youthful stories have been hailed as classics of the genre. Probably little published now, because in his old age he became a member of the Nazi Party.
* Dion Fortune was a British occultist of the highest degree of loopiness, but was also a 1930s imaginative novelist (mostly under the pen-name V. M. Steele)
* Ernest Thompson Seton was an American fore-runner of Baden-Powell and the Scouting movement. Lots of wood lore books, such as How to Catch Wolves, Animal Tracks and Hunter Signs, as well as some heart-tugging wild animal stories which might be suited to graphic novel / fantasy-makeover adaptation.
* Ernest Rhys, the British scholar and author of English Fairy Tales (1913). Some of the books he wrote might become the basis of a graphic novel, such as his concise historical introduction to London: The Story of the City and his novel Blackhorse Pit.
* Damon Runyon, a punchy and slick professional American short-story writer and newspaperman. He appears to have had a vast output over several decades. The slangy American wise-crack language may not be to today’s taste, but it seems likely that many of his plots would still hold up today.