Westlake explains the gap:
“I didn't know the reason then, but I know now. I didn't want to stop writing about him. I tried the next book three different times, but they all ground down. Now I see what happened. When I first came to New York, no one in my family had ever been involved in any of the arts at all. I didn't know anyone in the publishing world, I hadn't been to any of the right schools. I was a barbarian at the gates. The first Parker novel begins with him walking into New York and creating an identity for himself; saying, goddam it, here I am. That was me. That was 1961. But by 1974 I was successful, making a living, I'd sold movie rights for my books, I had a bit of a reputation, and it was very hard to keep that ‘outsider' muscle.”Read the full interview.
--Marshal Zeringue