Miss Kopp Investigates
By Amy Stewart. (Mariner Books, 304 pages, $15.99.)

Writers looking to keep their series fresh would do well to track what Stewart is doing with her Miss Kopp mysteries. Seven books in, they continue to surprise and delight, for several reasons: She can lean on the (heavily embroidered) experiences of actual people who lived a century ago. She has gradually shifted the focus of her books from trailblazing law enforcement officer/detective Constance Kopp to a trio of leads: Constance, bossy sister Norma and obstreperous baby sister Fleurette, who takes the lead for the first time in "Miss Kopp Investigates," helping a friend who's exploited by a con man. And Stewart cares about the lives that women really lived a century ago, especially the inventiveness they needed to face barriers erected to keep them at home, scrubbing potatoes.

Men still underestimate the Kopps in the breezy "Investigates" and the sisters still rise to the challenge with intelligence and determination, making it clear they have a lot of investigating left in them.