One Foot in the Grape (Cypress Cove Mystery #1) by Carlene O'Neil (Berkley Prime Crime mass market, 5 May 2015).
Penny Lively* left a successful career in journalism after an ethical disagreement with her editor. Serendipitously, she inherited the family winery from her Aunt Monique, and is running it with her niece, Hayley and longtime winery manager Connor.
Monique's elderly cousin Antonia Martinelli who owns a nearby property, a much larger winery, approaches her to ask for her help. Someone has been sabotaging random bottles of Martinelli wine, and she begs Penny to use her investigative skills to figure out who it is before the upcoming Autumn Festival.
There is no shortage of suspects: Antonia's two daughters are bitter because the winery will be inherited by their only brother, and her current manager is jealous of Antonia's young trainee.
Penny's inquiries have barely begun when she finds the body of Antonia's protegé, Todd, in Martinelli's grape crusher. Hayley is the prime suspect, having been the last to see him. Penny is certain that her niece is innocent, the search for the killer (who is obviously also the person ruining the wine) becomes even more crucial.
Penny is a smart and engaging protagonist, and the other characters are multi-layered and believable. California wine country is a charming location, and an inspired setting for this well-constructed mystery. I look forward to reading more of Penny's adventures.
The publisher has generously provided a copy of ONE FOOT IN THE GRAPE for me to give away to one lucky commenter in the US. Please don't forget to include an email address where you can be contacted if you win.
FTC Full Disclosure: Many thanks to the publisher for providing a review copy of the book.
*Apropos of nothing, Penelope Lively is a British author whose children's books I loved when I was of the right age.