The pros and contras of Mary Stuart's hotly disputed reputation: an adulterous whore, a threat to Protestantism, a murderous claimant to the throne of England, or a guileless martyr? Historians have been violently partisan since the 16th century when John Knox let it be known that ""the sun was not seyn to schyne two dayis befoir, nor two dayis after"" her arrival in Scotland in 1561. Cowan has edited the scurrilous as well as the hortatory, excerpted from four centuries of the still lively controversy, including testimonials of the poets Schiller, Swinburne, and Lamartine. Impeccably fair, Cowan balances friends and foes and concludes that Mary was not a zealous Catholic but a determined woman for whom ""political considerations came first."" The murder of Darnley is treated as a political assassination with Cowan sifting the evidence to the cautious conclusion that Mary's collusion in the deed cannot be proved and the authenticity of the Casket Letters remains in doubt. Mary's guilt in the various plots against Elizabeth, especially the Babington plot which led to her death, is more certain and the verdict of the trial ""was probably as just, as it was expedient."" The historical judgment here is also just, or at least judicious, and the historiographic presentation, which itself reads like an adversary proceedings is brisk and entertaining, though some of the more heavily Scottish passages (""Bot quhairto gadder we Argumentis as in a doutfull cace. . ."") are a real challenge.