"A master storyteller." -- A. S. Byatt The nineteenth installment in Sir Terry Pratchett's beloved Discworld series -- which has sold more than 23 million copies worldwide. There's a kind of magic in masks. Masks conceal one face, but they reveal another. The one that only comes out in darkness . . . The Ghost in the bone-white mask who haunts the Ankh-Morpork Opera House was...