Lynn Munroe has just posted an excellent essay and a thorough bibliography on Ben Haas in his website. Ben Haas was of course better known - at least here in Europe - as John Benteen, the writer of the delightful Fargo series. Lynn Munroe writes in length also about Haas's sex and sleaze paperbacks, many of which were previously unearthed.
I haven't read much Haas, but along with the Fargos I'll heartily recommend Big Bend as Richard Meade and some of his Lassiters and Cutlers. (Why not all of them? Because I have read only few. All have been consistently good.)
Oops! There's no Wikipedia entry for Haas! Work up one!