Apparently I remember very little from the movie of Double Indemnity, other than Fred MacMurray. Because the rest only vaguely rang any bells.
But these three novels are solid film noir, with a touch of intense family drama. The main characters are never particularly innocent (although Mildred Pierce is fairly sympathetic for most of her eponymous novel), and most plot to commit desperate crimes that they think will be perfect.
Unfortunately, as any good noir writer would tell you, those plans always rely on absolute trust between the conspirators, and that eats away at relationships and plans.
So for morality tales written stylishly, I would recommend these three.