At first there seems to be no particular reason for this short biographical study, focusing on Mozart's reationship with wife Constanze: Carr, in literate but unremarkable prose, sketches in the courtship and marriage, quotes at length from the well-known letters, and arrives at an unfavorable--but far-from-unprecedented--view of plain, opportunistic Constanze and her scheming mother. (""They were taking Mozart away from his state of bachelor independence by force, that is by encouraging, perhaps starting, rumours about his dalliance with Constanze, by the threat of legal action. . . ."") Then, however, when turning to the last four years of Mozart's life, Carr starts building a case for a quietly wild theory about the composer's much-debated demise. Mozart's hard-to-explain money problems? Perhaps, Carr implies, he was spending large sums on his rumored mistress--Magdalena Hofdemel, wife of a chancery official. (Meanwhile, Constanze--who ""did not love him sincerely during these last years""--was probably carrying on with music-student Franz Xaver Sussmayr, who may have fathered her last child.) Next, Carr examines the medical evidence, suggesting that ""death by poison"" is a likelihood. And what about Mozart's shoddy burial--which (though explained away by other biographers) seems to indicate, for Carr, both Constanze's hostility and a general attempt at coverup? The solution? Mozart was poisoned by jealous Herr Hofdemel, who did indeed commit suicide around the time of Mozart's death. Far from fully plausible, sometimes slippery in its gentle, sneaky speculation--but an intriguing little diversion for Mozartians who are weary of the much-recycled Salieri theory.