 From 1561 he was also a cardinal; although this appointment was in pectore (not made public) he is sitting in the "audience" posture (reserved normally for Popes and cardinals).The book standing up is the "La Practica della Perspettiva", Barbaro's treatise on artistic perspective.The other volume on the table is Barbaro's "Commentary" on Vitruvius' "De architectura", which has illustrations by Andrea Palladio.