Sources:
http://www.newcriterion.com/archive/17/may99/auden.htm
http://www.audensociety.org/criticism.html
http://www.kirjasto.sci.fi/whauden.htm
http://www.island-of-freedom.com/AUDEN.HTM/
http://pages.infinit.net/noxoculi/auden.html/ (In french)

Books:
"Auden And Christianity: A Spiritual Biography." (Arthur KIRSH)
Famous for his declaration that "Poetry makes nothing happen," W. H. Auden thought quite differently about Christianity, which he regarded as possessing a marvelous power to change human lives.

Inexplicably, however, critics have largely neglected the effects of Auden's mature commitment to Christianity. Kirsch remedies that neglect with this much-needed study of how Auden's religious beliefs shaped his artistic vision. He depicts Auden as an often perplexed and frequently heterodox believer, one who wrestled with profound doubts. But whatever his theological irregularities, Auden voiced a Christian faith both intense and poignant in poems such as "For the Time Being" and "Horae Canonicae." And it is a Christian humility and self-discipline that Kirsch sees in Auden's oft-noted metrical virtuosity. Neither a dogmatist nor a homilist, Auden always wrote as one simply overwhelmed at both the one-time miracle of divine love manifest in Jesus and the ongoing miracle of human love expressed in forgiveness and acceptance. A fascinating blending of aesthetics and theology.

"W.H.Auden" ( Richard Davenport-Hines)
Using his literary and analytical backgrounds, Times Literary Supplement reviewer Davenport-Hines presents a tremendously thorough and, indeed, intimate portrait of Wystan Hugh Auden, one of England's most notable poets. Unlike many contemporary biographers who try to scrounge up some new information, dazzle with some brilliant insight, or even shock with bizarre theories, Davenport-Hines is concerned with truth, as much as it can be ascertained, and in offering the most accurate and comprehensive view of Auden's life that he can. In so doing , he acknowledges prior critics' and biographers' contributions and discoveries. Yet he mostly turns to Auden himself and to the journals, letters, prose, and poetry that reveal so much about his personality. From the quirky influences of childhood stories to deep-seated sexual obsessions to bold statements of ambition and intent, Auden's words are skillfully tied together by Davenport-Hines, making this book a valuable piece of scholarship and an engaging study of Auden's life

These sites presents the life of Auden. The first is a good overview, but the second provides more details and interesting information to understanding his evolution.

Summary:
AUDEN was born in York in 1907 and moved to Birmingham very soon. He was educated at Christ church, Oxford. Deeply influenced by the poetry of Thomas HARDY, ROBERT FROST, WILLIAM BLAKE and GERARD HOPKINS, he was also interested in English verse. His remarkable precocity for poetry was immediately apparent. By 1928, Auden begun to be concerned about his homosexuality. The influence of the factor was to be significant in his life and work. His departure for Berlin is largely explained by this aspect of his life.
The same year he published his first book of verse and became famous in 1932 with "the orators" and "the dance of death". Without being a member of communist party he was, like most intellectuals and artists of the 1930's aligned with these far-left movements. Anyway it is possible to observe at this stage his main concern,which was to remain the same throughout all his life: the worldwide economic distress which leads to human distress.
In 1937 he was committed to the century's struggles since he joined Spain to observe the fighting between the democratic loyalist armies and the right-wing forces of Franco.
In 1939, Auden's paradox emerged with his departure for the USA with Christopher ISHERWOOD. This year was very important because of his meeting with Chester KALLMAN and for his production that year. Parallel with Hitler's actions, Auden wrote one of his greatest poems like "September 1, 1939" .
By 1940, Auden had written"The Sea and the mirror", "the double man" "For the time being" and "the age of anxiety". It is certain that at this stage a change was under way. The influence of Modernity was already his object of denunciation especially in "For the time being", a Christmas oratorio of religious commitment in the midst of world war.
From 1946 to 1958 Auden served as a judge and editor of the Yale series of Younger poets
He wrote several middle-length meditative sequences of shorter poems: "Bucolics", "Horae canonicae" and one of his greatest poems "the shield of Achilles", a chilling commentary on the pervasiveness of cruelty.
From 1954 to 1973 he was chancellor of the Academy of American poets.
He died in Vienna in 1973.