Watching the wide and nearly endless stream of books about Wagner, one might not pay much attention to Geoffrey Skelton's latest effort--his fifth relating to the composer. But "Richard and Cosima Wagner" marks the beginning of a new era in Wagner scholarship when any scholar can have full access to millions of words of primary sources that were previously available only fitfully to a chosen few. If we are lucky, the timely arrival of this volume, which neatly skims the cream from the new material, will do something to stem the flood. We are not likely to be so lucky.

The world certainly knows more than it needs to about the love and marriage of Richard and Cosima Wagner. While great question marks hang over the lives of composers ranging from Alkan to Zelenka, while scholars lament the serious gaps in our knowledge of Beethoven's life or Scott Joplin's, there is a glut of Wagner material. Open Cosima's voluminous diaries at random, and you can learn that a mosquito disturbed their sleep during the night of Dec. 4/5, 1881, during a sojourn in Sicily, that Wagner was critical of beards ("those emblems of the animal in men") in his lunch-time conversation the next day, and that in the evening he was so irritable that she felt compelled to "call upon the God within me to give me strength against evil spirits."

This kind of material is available for nearly every day in the last 14 years of Wagner's life, and it can be supplemented from his own much less thorough diary and voluminous correspondence--though Richard's and Cosima's letters to one another were systematically and almost completely destroyed. The Cosima Wagner diaries were kept secret (with a few small exceptions) for nearly a century after she stopped writing them, but they are now published and translated, and they have the power to generate other books endlessly. Along with retellings of the epic story of the building of Bayreuth, psychoanalyses of Wagner's mad patron, King Ludwig II of Bavaria, discussions of the trauma suffered by Cosima because she was the neglected daughter of Franz Liszt and a French countess, and new looks at the familiar story of how Wagner wooed and won the wife of a fellow musician, close friend and strong supporter, Hans von Bulow, consider the possibility of such titles as: "The Effects of Mosquitoes on Wagner's Equanimity"; "Wagner on Beards"; "Cosima Wagner and the Spirits Within."

Skelton has a head start on the competition because he got to the material first; he was the English translator of Cosima's diaries, and he must know the material as well as anyone living--better, perhaps, than Cosima, who merely had to dash it off, not translate and annotate it. He certainly has details that must have been unknown to Cosima about Wagner's abortive affair with the French writer Judith Gautier near the end of his life, and he relates them conscientiously, objectively and with admirable thoroughness.

One such anecdote sums up much of Wagner's personality in its total, unconcerned self-centeredness: "In 1876 Wagner arranged for a seat in the festival theater between Judith Gautier and her lover, Ludwig Benedictus to be kept empty for him, and, slipping into it when the lights went down, he held her tightly and whispered to her: 'I should like to listen to all my works in your arms.' " Richard and Cosima had by then been married for six years, she having borne him three children before they solemnized the union.

Skelton does not bother to stop and deplore what is deplorable in the subject of his biography, nor does he waste much time admiring again what has already been so often admired. His concern is primarily with facts: to examine them in their confusing abundance, to sift from that abundance what is most useful and interesting and to present it in a reasonable, orderly style. He has done it well, keeping the material of permanent interest while he eliminates the mosquitoes, beards and evil spirits. The work is largely a condensation--and thereby an enrichment--of the diaries he has already translated, and in addition, he has a critical detachment that is both necessary and refreshing. "The diaries," he tells us, "must be approached with a certain degree of skepticism. Cosima wrote them avowedly for the benefit of her children, and thus she strove always to present Wagner in the best possible light, and to conceal from them aspects of his behavior which may at times have caused her sorrow."

As for the importance of the marriage he chronicles, he puts it succinctly and cogently at the beginning of his book: "Without this marriage the world would possibly never have seen the final products of Wagner's genius which emerged in its course: the completion of 'Der Ring des Nibelungen,' the building of the festival theater in Bayreuth, the composition of 'Parsifal.' Cosima's contribution was far more than that of providing Wagner with a settled family existence in which to pursue his work, though that in itself was an important factor; she was also his active assistant in all his undertakings."

It was a collaboration nearly unique in the history of the arts, and it deserves to be widely known in approximately the amount of detail Skelton gives it.