You know the truism that asserts nobody understands a marriage except the two people in it? Two new books with similar titles suggest that may not be so true.

Strong Passions
Strong Passions

"Strong Passions," by Barbara Weisberg, paints an astonishingly vivid portrait of the marriage of Peter and Mary Strong, particularly when you consider that it was more than 160 years ago. Even at that remove, the details are shocking: Mary had an affair with her husband's brother Edward, Peter may have forced Mary to have an abortion, Mary disappeared without a trace on the eve of the Strong divorce trial, taking one of their two daughters with her.

Using letters, court testimony, diary entries and even the novels of Edith Wharton (who was a relative of the couple), historian Weisberg is able to go into incredible detail and draw conclusions about matters that New York courts were unable to settle. It's a gripping portrait of how things have changed when it comes to the sexes. (In the 1860s, a jury decided whether a man and woman could be divorced and, if the divorce were granted on the grounds of adultery, the adulterer would not be allowed to remarry until their former spouse died.) And how things haven't changed all that much.

Similar themes emerge in a true crime account of more recent adultery gone amok, "Guilty Creatures." Journalist Mikita Brottman looks at two deeply religious Florida couples who were friends, Mike and Denise Williams and Brian and Kathy Winchester. Things take a turn when the men go on a 2000 fishing trip from which Mike, supposedly swallowed by an alligator, never returns.

Guilty Creatures
Guilty Creatures

Brottman persuasively cites James N. Cain's noir classic "Double Indemnity" to illuminate where the real-life relationships went astray (as in the novel, one character is a trusting insurance salesman and another is good at figuring out how to make the most of a recent policy). Brottman gets a little too cocky — muddying her book with less-pertinent references to, for instance, "Hamlet" — but, like Weisberg, she has the ability to make sense of seemingly inexplicable behavior by zeroing in on the banal desires that lead to it.

Strong Passions

By: Barbara Weisberg.

Publisher: Norton, 299 pages, $28.99.

Guilty Creatures

By: Mikita Brottman.

Publisher: One Signal, 288 pages, $28.99.