One book I got over the Christmas period was Sin-A-Rama, published by Feral House in the US. I'd been told about this by commenters as a great source of information on the sleazy pulps and the people behind them. It truly is a treasure trove, especially regarding covers... (click for bigger versions of the following spreads)
The second spread features an alarming clown-featuring cover by Eric Stanton, as well as another by an artist I'd never heard of before: Elaine Duillo. (And who knew there was such a demand for clown sleaze? And if you did know, please keep it to yourself.)
Among her many other covers, Duillo also produced one that I would have included in my wrap-up of Zola sleaze, if only I had known of it.
Here are some more Duillos--like Robert Bonfils, she's someone with real technical skill and an eye for design who spent her professional life in the artistic gutter, without letting it squash her visual flair.