Papal history without pomp, circumstance, or spirituality--as chilly novelist Condon (Prizzi's Honor, etc.) details the largely factual 1390-1415 story of Baldassare Cossa, a soldier/pimp/entrepreneur who became mercenary Pope John XXIII. . . and the fatalistic, much-betrayed pawn of rising banker Cosimo di Medici. The off-and-on narrator here is Franco Ellera, Jewish slave to the Cossas, a pirate-family of Naples; and when young Cossa is sent off to Bologna to begin studies for a lawyer/prelate career, Franco goes along as sidekick. But, while rising in academia and Bologna politics, Cossa also pursues his other life--as rake, pimp, thief (stealing a hoard of Papal gold), soldier-of-fortune. An atheist who has never taken holy orders, he becomes a cardinal largely because of his battlefield triumphs in fending off the current pope's enemies. And along the amorous way (317 conquests, not including courtesans), Cossa falls madly in love with two women: Catherine Visconti, wife of the Duke of Milan; and Decima Manovale--the super-courtesan who, working for the Medici Bank, uses her four daughters as bedroom diplomats and plots Cossa's way to the Papacy (as a ""conciliar"" pope to end the church's great Schism, an alternative to the feuding Rome/Avignon pontiffs). Cossa initially declines the opportunity, however--and Alexander V becomes the first conciliar pope. (Says Decima: ""Cossa, you rotten Neapolitan shit of Satan, we almost killed ourselves getting the papacy for you!"") Then Decima secretly poisons both Alexander and Catherine, who was enticing Cossa to purely temporal ambitions; Cossa is ""trapped in the papacy""; manipulated by the Medicis, he must now woo King Sigismund of Hungary, battle for Rome against King Ladislas of Naples (soon another poison-ee), and contend with reformist challenges from John Hus of Bohemia. But, when the Medicis double-cross Cossa at the long Council of Constance, the Pope will find himself in the same dungeon with Hus--forced to abdicate. . . though not before avenging himself on Decima and her daughters. With slangy anachronisms and utter cynicism, Condon sometimes offers a bouncy--if only half-convincing--picture of the Church as Mafia. And he does manage to digest large chunks of complex Church-in-Schism history. But no one here, including ruthless-yet-passive Cossa, is even roughly sympathetic; the melodramatic episodes (some purely fictional) get lost amid all the historical detail; and, though free of the verbose stateliness usually found in pope novels, this lowdown, relatively breezy chronicle is more intriguingly informative than richly entertaining.