In a couple of recent posts, I’ve mentioned rediscovered works by well-known writers. There’s the novel by Walt Whitman (http://schatjesshelves.blogspot.ca/2017/03/walt-whitman-novel-discovered.html) and a short story by F. Scott Fitzgerald (http://schatjesshelves.blogspot.ca/2017/03/new-f-scott-fitzgerald-story.html).
The fall 2016 issue of The Strand magazine included a newly discovered short story entitled “The Haunted Ceiling” by H. G. Wells written in the mid-1890s. The story is about a man driven mad by a woman’s ghost in his ceiling: https://strandmag.com/product/unpublished-h-g-wells-story/. (This plot sounds similar to Edgar Allan Poe's "The Tell-Tale Heart" published in 1843.)
Last fall, The Tale of Kitty-in-Boots, a new children’s story by Beatrix Potter, was published. It’s about a serious, well-behaved young black cat, who leads a daring double life defeating villains. For the story of its discovery, read http://www.usatoday.com/story/life/books/2016/01/26/rediscovered-beatrix-potter-story-delight-new-generation-kids/79348750/.
2015 saw the publication of What Pet Should I Get? That’s a Dr. Seuss children's book believed to have been written between 1958 and 1962. The book chronicles the adventures of Jay and Kay from Seuss' One Fish Two Fish Red Fish Blue Fish in their attempts to buy a pet. The New York Times wrote about its discovery in a box: https://www.nytimes.com/2015/07/22/books/dr-seuss-book-a-discovery-in-a-box-and-then-a-reconstruction.html?_r=0.
Of course, not all works by writers find their way into print. Here’s an article about books you will probably never be able to put on your shelves because they've either been stolen or destroyed: http://mentalfloss.com/article/92922/unpublished-manuscripts-7-famous-authors.