“The Relic Master” is an inspired piece of literary gymnastics. We are in Northern Europe in 1517 and an outraged, constipated monk named Martin Luther is calling time on the corruption — sexual, financial and spiritual — of the Roman Catholic Church. The problem is exquisitely summed up in Buckley’s opening chapter, set at a relic fair in Basel. On sale is a dazzling array of sanctity: hundreds of bits of saints’ and martyrs’ skulls, teeth, bones and hair; iron bars from torture grilles; whips and thorns, as well as nails, wood and blood from the crucifixion; even a vial with drops of the Virgin’s breast milk. Capitalism may be in its infancy, but relics are a healthy source of revenue for the church and private collectors, and in line with market forces, supply rises to meet demand. (Five hundred years on, one can, of course, still find similar relics in churches all over Italy.)