The author is a Dean of Corpus Christi College, Cambridge, where he lectures on philosophy, writes about Nietzsche, and reviews for Classic CD and the Times Literary Supplement. As such, and as he admits, his views of Wagner are admiring but iconoclastic, and frankly amusing.
Supplies a thorough understanding of Wagner's life and work, with somewhat unorthodox analyses of his music and dramatic purposes.
Even with only a rudimentary acquaintance with Wagner's operas, I found the book highly informative and enjoyable.
My own interpretation of Tanner's analysis (and he never says this in so many words, but I think the implications are there) is that Wagner was looking for the meaning of Gospel Love and Sanctified Marriage, but found the connection to Christianity completely unacceptable, and so turned to pagan mythology for his inspiration, resulting in the psychological and spiritual muddle that Tanner documents. The Tristan / Isolde and Siegmund / Sieglinde couplings of illicit passion are counter-posed to the banality of the Meistersinger's more prosaic but licit romance, while the renunciations of Parsifal and Lohengrin are somewhat in the middle.
Tanner thinks that Wagner's heroes are looking for redemption (usually from their own immoral acts), and his heroines looking for someone to redeem (in the worst tradition of abused women everywhere), -- but no one is looking for redemption through the atonement of Christ. ( )

A chronological review of all of Wagner's operas, including Die Feen, although I would have thought everything that could profitably have been said about Wagner's first opera had been said long, long ago. Tanner is particularly eager to defend Wagner from illegitimate criticism that conflates biographical (Wagner was often a bad boy) and ideological (Wagner was a racist) prejudice with judgment on aesthetic value. I, for one, certainly take his point and need no further special pleading. Tanner's at his best with his extended discussion of the Ring. I'm taken with his view that there is no ultimate meaning to this almost infinitely complex mega-drama -- or that if there is, the meaning has to do with the transcendent power of delusion. Ultimately, though, all considerations of Wagner (or any serious composer) without detailed musical analyses are self-limiting and can provide only superficial insight. ( )

British academic philosopher Tanner has written on music for the Times Literary Supplement and is author of Nietzsche, a volume in the "Past Masters" series from Oxford University Press (1994). Nietzsche wrote a lot about Wagner, joining a flow of opinions that became a river long ago. Tanner quotes him here, mainly in order to argue with him and many others who find fault with the complicated, controversial German music dramatist. Opening by harshly explicating some Wagner criticism as "inane," "outrageously unfair," and "priggish," Tanner then spiritedly discusses all the operas in chronological order, focusing upon effects he feels their characters, stories, and music are meant to have on thoughtful members of the audience. When these effects are contradictory, Tanner self-consciously argues with himself. A short bibliographic essay provides leads to still more views. A warm-hearted, occasionally hot-headed defense of Wagner; recommended for balance.

From Kirkus Reviews
Tanner, a Cambridge philosopher and opera critic for the Spectator, offers analyses of the plots of Wagner's operas, the intellectual themes projected by them, and an evaluation of the music that is (for most of us) their justification. Tanner's discussion of The Ring is superb and makes an otherwise very uneven book required reading. He often overstates (arguing, for instance, that Tristan is one of the two great religious works in Western music, along with the St. Matthew Passion), and he

While no one would dispute Wagner's ranking among the most significant composers in the history of Western music, his works have been more fiercely attacked than those of any other composer. Alleged to be an unscrupulous womanizer and megalomaniac, undeniably a racist, Wagner's personal qualities and attitudes have often provoked, and continue to provoke, intense hostility that has translated into a mistrust and abhorrence of his music. In this emphatic, lucid book, Michael Tanner discusses why people feel so passionately about Wagner, for or against, in a way that they do not about other artists who had personal traits no less lamentable than those he is thought to have possessed. Tanner lays out the various arguments made by Wagner's detractors and admirers, and challenges most of them. The author's fascination for the relationships among music, text, and plot generates an illuminating discussion of the operas, in which he persuades us to see many of Wagner's best-known works anew--The Ring Cycle, Tristan und Isolde, Parsifal. He refrains from lengthy and detailed musical examination, giving instead passionate and unconventional analyses that are accessible to all lovers of music, be they listeners or performers. In this fiery reassessment of one of the greatest composers in the history of opera, Tanner presents one of the most intelligent and controversial portraits of Wagner to emerge for many years.