Obscure forgotten literature is pretty much all I've read. IME the best works of literature more often than not get completely overlooked. I have a theory about that but it can wait for a different post. The best thing to know here is where to find all these amazing forgotten books. Here are some of my my favorite publishers which entirely focus on forgotten masterpieces of literature, many of which have not been published in English in many decades if ever.
https://wakefieldpress.com/schwob_monelle.html
This first one is my favorite book of all time which Borges cited as inspiration along with the entire French Symbolist movement.
https://www.snugglybooks.co.uk
I cannot emphasize enough just how great many books from these publishers are in stark contrast to how totally unknown they are. The book I link at the top The Book of Monelle was called the Bible of French Symbolism and was incredibly popular in the 1890s-1910 but today its completely unknown. I really don't get it.