I know I read John D. MacDonald's APRIL EVIL (1956) for the first time back in the 1980s. I re-read it recently while recuperating from hernia surgery. It's as good as I remember it.
The plot is basic caper material. A rich old eccentric keeps a million dollars in cash in a vault in his two-story, stone house in the small town of Flamingo, on Florida's gulf coast. A gang of professional crooks, Harry Mullin, Sal, The Ace and Ronnie (the last, a hired killer), come to town to plot the robbery. At the same time, the simmering greed and corruption of the old man's heirs, Dil and Lorena, comes to the surface and they decide to try and con the old man out of his money. And a nosy kid who lives next door to the house the crooks have rented, learns the truth about his new neighbors.
All of the characters are well drawn as is the sense of time and place. My only complaint, and it's a slight one, is that after so much build up, the actual heist is over fairly quickly and so is the book. Still, this is one lean, mean, tough little piece of vintage pulp crime fiction. It would have made a helluva good movie in the 1950s. Recommended.