Conversation so far:
What was M. John Harrison's first novel?
The Committed Men is M. John Harrison's first novel.
Did M. John Harrison write in any other genre before writing Science fiction?
In M. John Harrison's early years, his hobbies included writing pastiches of H. H. Munro.

Question: How popular were his first stories?
Self-contained rewrite: How popular were M. John Harrison's first stories?