Conversation so far:
Does Lord Voldemort appear in Harry Potter and the Half-Blood Prince?
Lord Voldemort does not appear in Harry Potter and the Half-Blood Prince, although his presence and actions are felt
Were there any flashbacks for Lord Voldemort in Harry Potter and the Half-Blood Prince?
Yes; in a series of flashbacks, the author uses several chapters as exposition to establish Lord Voldemort's backstory

Question: Who was the author of Harry Potter and the Half-Blood Prince?
Self-contained rewrite: Who was the author of Harry Potter and the Half-Blood Prince?