You won’t be surprised to learn that Sheldon Lord and Lawrence Block were one and the same. Block has always been a wildly prolific writer, which is one reason for the pseudonym. Here’s a bit about this book with two titles and covers from blogger James Reasoner:
Like LUCKY AT CARDS, A DIET OF TREACLE is a Hard Case Crime reprint of an early, pseudonymous novel by Lawrence Block. In this case, the book was originally published by Beacon Books in 1961 under the title PADS ARE FOR PASSION and the pen-name Sheldon Lord. It’s the story of Joe, Shank, and Anita, three young people who become involved in the hipster drug scene in Greenwich Village circa 1960.
Party on, Sheldon. Party on, Lawrence.
Here are the covers side-by-side: