This is one of the old Lawrence Block sleaze titles Hard Case Crime has been reprinting. Killing Castro was somewhat disappointing, and so was this. A Diet of Treacle is a ménage à trois between two beatnik guys (one a loser, other a criminal) and a girl who'd like to be a beatnik. The book is not really a crime novel, it's more a novel with a crime. The actual plot starts only after the middle part, but Block writes so smoothly it's not a huge problem. The problem lies with the fact that the plot is too thin after all - and that there's too much of the beatnik slang, with everything being cool, solid or hip. The ending is good, though, real noir stuff.
The book was first published as Pads Are For Passion (Beacon, in the early sixties), but A Diet of Treacle (name snatched from Lewis Carroll) was Block's original title. This kind of information is something I'd really like Hard Case Crime would tell at their website. The book was first published under the Sheldon Lord by-line and I already started reading Sheldon Lord's Kept that was written also by Block. Seems pretty solid (sic) by the first 50 pages.