Bats Fly at Dusk is a variation on the hard-boiled detective tradition of American mystery writing. Sam Spade of The Maltese Falcon (1930) and Mickey Spillane's Mike Hammer of several novels, including I, the Jury (1947), are both examples of hard-boiled detectives. They are tough, know the seamy side of life, and enjoy the company of good-looking women. They also follow a code of ethics that while not strictly adhering to the letter of the law, means that they must pursue mysteries to the bitter end. Spade, for instance, turns a woman he cares for in to the police because a private eye is supposed to do something about the murder of his partner, no matter who gets hurt.

The Bertha Cool/Donald Lam novels have fun with the hard-boiled detective story. Cool is plainly unethical; her code on honor extends little further than her pocketbook, even though...