Conversation so far:
Can you provide me with a little information on the religion of H.P. Lovecraft?
Lovecraft himself adopted the stance of atheism early in life
Was H.P. Lovecraft disliked for being an atheist?

Question: Can you tell me what that letter was about?
Self-contained rewrite: Can you tell me what the letter from H.P. Lovecraft to Robert E. Howard was about?