Symbols of fleeting happiness and lasting sadness: such are the butterflies and columbines in Pisanello’s portrait of Ginevra, first wife of Sigismondo Pandolfo, says Hugh Bicheno in Vendetta: High art and low cunning at the birth of the Renaissance (Weidenfeld & Nicolson, £25 (£22.50); 978-0-297-84634-5). The book explores the “military” Renaissance — a period of constant warfare among the Italian states, which yet produced lasting works of art