Vince Keenan kindly read a Liquidator novel so I wouldn't have to. I noticed in the picture that the book was published by Ace/Charter. The Liquidator novels I own were published by Award Books. Maybe when Award went out of business, Ace took over some titles. Or maybe the Liquidator novels were so good that Ace reprinted them. As I mentioned to Vince in my comment, the idea of a lone vigilante trying to wipe out the Mafia is so startlingly original that Ace probably couldn't resist. At any rate, here's one of the Award Books covers.