This is book number 19 in the Discworld series.
The Ghost in the bone-white mask who haunts the Ankh-Morpork Opera House was always considered a benign presence—some would even say lucky—until he started killing people. The sudden rash of bizarre backstage deaths now threatens to mar the operatic debut of country girl Perdita X. (nee Agnes) Nitt, she of the ample body and ampler voice.
Perdita's expected to hide in the chorus and sing arias out loud while a more petitely presentable soprano mouths the notes. But at least it's an escape from scheming Nanny Ogg and old Granny Weatherwax back home, who want her to join their witchy ranks. Once Granny sets her mind on something, however, it's difficult—and often hazardous—to dissuade her. And no opera-prowling phantom fiend is going to keep a pair of determined hags down on the farm after they've seen Ankh-Morpork.
Sir Terry Pratchett was the internationally bestselling author of more than thirty books, including his phenomenally successful Discworld series. His young adult novel, The Amazing Maurice and His Educated Rodents, won the Carnegie Medal, and Where's My Cow?, his Discworld book for “readers of all ages,” was a New York Times bestseller. His novels have sold more than seventy five million (give or take a few million) copies worldwide. Named an Officer of the British Empire “for services to literature,” Pratchett lived in England. He died in 2015 at the age of sixty-six.