It’s hard to know who to believe. That’s a good thing.

The unreliable narrator can frustrate readers a bit as they try to figure out just who to believe. But this literary device also can make for some intriguing stories, as Liv Constantine shows in her third, exciting novel.

Constantine, the pseudonym for sisters Lynne Constantine and Valerie Constantine, again shows a knack for the psychological thriller that they established in their best-selling debut, “The Last Mrs. Parrish.” It is easy to overlook the shallow prose when strong storytelling draws in the reader — hook, line and sinker.

“The Wife Stalker” alternates between two desperate women. Joanna loves her two wonderful children, Evie and Stelli, and believes her marriage to charismatic attorney Leo Drakos is secure and happy.

Piper Reynard, a new resident of Westport, Connecticut, has decided she wants Joanna’s family. Piper has opened a rehab and wellness business, immersing herself in the affluent community by joining the yacht club. Piper, who has changed her name and scrubbed her internet identity, is hoping this move will be permanent as she’s tired of finding “new places to hide,” especially since the rather untimely deaths of her husband and stepdaughter in California.

Joanna knows that Leo has been suffering from depression and believes that the affair with Piper is part of that. She hopes that he will return to her and, most importantly, knows he loves the children. Piper has other ideas as events

Sisters Lynne and Valerie Constantine write under the pseudonym Liv Constantine.

take a dark turn. Although worried about the safety of Leo and her children, Joanna finds herself alone as both her therapist and emotionally cold mother believe she is just being paranoid. Obviously, they never heard the term gaslight.

The reader’s allegiance often shifts from Joanna to Piper as each narrates, showing a different perspective. Each believable twist draws in the reader as Constantine keeps the suspense high. A clever twist pulls “The Wife Stalker” in a unique direction that readers will savor.

‘The Wife Stalker’

By Liv Constantine. Harper, 320 pages, $27.99

For the week ended June 13, compiled from data from independent and chain bookstores, book wholesalers and independent distributors nationwide.

— Publishers Weekly

BILL MILES