Bantam of the Opera by Mary Daheim

Bed-and-breakfast hostess Judith McMonigle Flynn isn't exactly bellowing "Bravo!" over the news that obnoxious opera star Mario Pacetti and his entourage are coming to stay at the Hillside Manor. The world-class tenor is a renowned pain-in-the-neck—a bloated buffoon who could easily eat her out of house and home. So when the puffed-up, would-be Pavarotti inadvertently drinks poison and falls down dead on his tosca, accusing eyes turn to Judith and her amateur sleuthing partner, cousin Renie. Now it's curtains unless the cousins can unmask the real culprit—before a killer's final, fatal encore.