Trove of Clarke's Goodies: "The Collected Stories" by Arthur C. Clarke
There are many early 20th century writers whose SF and fantasy continue to be read today.
The very successful literary writer James Branch Cabell would find half his novels categorized as fantasy today, including his most famous, Jürgen. Though he predates the period, the equally talented Robert Chambers was an excellent literary fantasist; his book the King in Yellow had vast influence over the 20th century "weird" fiction sub-genre including the lesser writer H. P. Lovecraft whose works are still enormously influential.
If you're into stuff like this, you can read the full review.
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