In our age of elasticated leisurewear, ready meals and box sets on telly, it is exhilarating to read about people who would come down to dinner in peacock-feather head-dresses, swathed in large snakes and dripping ornamental chicken blood. The Marchesa Casati has a loyal cult following and her bizarre style still influences fashion designers; but by placing her alongside two sisters in scandal in this triple biography, Judith Mackrell has done something very clever and entertaining.