Jules Verne!
He wrote science fiction novels with exceptional creativity. Some books by Jules Verne are: "A Journey to the Center of the Earth" and "Twenty Thousand Leagues Under the Sea".
Another good author is H.G. Wells. Some great books by him are: "The Time Machine" and "War of the Worlds".
The macabre/ scifi stories by HP Lovecraft were written well before the 50's. He didn't write full novels, but his novellas were a mix of scifi and macabre. Check out the Color out of Space, the Walls of Eryx, and the call of Cthulhu.