It takes considerable courage and incontrovertible evidence to propose, as Bossy (History/Univ. of York) does, that Giordano Bruno, an Italian ""national saint"" burned at the stake in 1600 for defying the Pope, spent three years (1583-86) as an anti-Catholic spy at the pro-papal French Embassy in London. According to Bossy, Bruno--an excommunicated Neapolitan friar who sometimes used the alias of a priest named Henry Fagot--served the religious needs of the ambassador's family and of the English Catholic sympathizers who found refuge at the embassy, birthplace of the conspiracy to assassinate Elizabeth I and release Mary, Queen of Scots, imprisoned for the past 19 years. As Fagot, Bruno claimed that he learned of the plot during confession, leading to the arrest, torture, and ultimately the execution of several English noblemen and contributing to the decision to execute Mary as well. If this story is true, then Bruno was not just a spy but a fraud, impersonating a priest, and a traitor, betraying the French king and the ambassador, and all of this for rather vague reasons--neither for money nor power but to undermine the credibility of the papacy and because it appealed to his taste for practical jokes. From this story, it is difficult to tell how Bruno acquired his reputation for brilliance, charm, wit, courage, and integrity, for Bossy depicts a ""smart operator"" and a ""dishonorable"" one, argumentative, abrasive, the author of ""soporific"" dialogues whose speculations on science and cosmology were eccentric and unoriginal. Regrettably, the significance of Bruno and even of the conspiracy is lost in Bossy's presentation--obscure, convoluted, turgid, weighted with chronologies, false clues, obfuscation, irrelevant letters, artificially designed mysteries--such as a whole chapter arguing for the ""coincidence"" of Fagot and Bruno's similarities when Bossy is about to reveal that they are the same man. However correct his facts, however indisputable his conclusions, Bossy compromises them by his melodramatic presentation--which is probably more suitable to fiction. A bewildering and frustrating read.