IN EASTER WEEK in 1938, Simone Weil sat in the Benedictine abbey at Solesmes, soaking up the plainchant. She needed it. With her life and work at an impasse, stricken by intense and debilitating headaches, and as Europe stood on the verge of catastrophe, she recited to herself a poem she later declared "the most beautiful poem in the world".

Under the spell of that poem, she felt, to her astonishment, "a presence more personal, more certain, and more real than that of a human being". The encounter changed her life, and the lives of many since, because it was the start of her journey to become one of the great writers of the 20th century - a unique modern mystic. When I first read that story in my twenties - already captivated by Weil's work - I found myself nonplussed by its key detail. The "greatest poem in the world", Weil said, was George Herbert's "Love III".

I did not doubt the power of poetry. Donne's "Batter my heart . . ." could change a life, I was sure; but Herbert seemed to me to lack the raw voltage of Donne. Like many of my generation, I was introduced to both Donne and Herbert at school through Helen Gardner's Metaphysical Poets anthology. And, like many, I was captivated by Donne, but found Herbert's poems, by comparison, quiet and pious.

"Young people prefer Donne, because he writes about sex, and Herbert never does," Herbert's biographer, the Very Revd John Drury, says. And it is hard to argue with that.

DRURY is Chaplain and Fellow of All Souls College, Oxford, a literary and biblical scholar whose remarkable Music at Midnight (Allen Lane, £25) is the fruit of years of painstaking work on Herbert's life and poetry. Sitting at a book-stacked table in his study, with Herbert's Collected Poems open on a book stand in front of us, I make my confession to John.

Since my teens, I have loved Donne, and respected Herbert. But in recent years, I have started to see them in reverse. The harder you look at Donne's work, the more control and mastery you see there. In Herbert, the formal virtuosity seems borne out of urgency and desperation. His poems are exploratory, risky ventures, full of turmoil and uncertainty, attempts to control the volatility of his inner life. In the words of Robert Frost, each poem is "a momentary stay against confusion", and, in that, they seem vital, intimate.

"Herbert's is a quieter voice than Donne's; that's true," Drury says, "but he's far more affected by doubt and anxiety. His outer life was pretty uneventful, but his inner life was no picnic." It is a point made by several reviewers about Music at Midnight: the way this book - rooted as much in the poems as the life - renders Herbert's inner turmoil, and his struggles with God and himself, so vividly, despite the apparent lack of biographical "events".

Herbert's was a life of outward comfort and privilege. Educated at Westminster School and Cambridge, he had a glittering university career, and looked set to become a wealthy establishment figure before a crisis of vocation sent him into Anglican ministry. He married late, but happily, and died at the age of 39, bequeathing a batch of poems to his close friend Nicholas Ferrar, who became the custodian of Herbert's work.

BUT, as Drury's book makes clear, you cannot understand the making of Herbert the poet without paying attention to his extraordinary mother.

Magdalen Herbert was (for most of George's childhood) a widow bringing up ten children. There was family money, which helped Magdalen to move the family to Oxford and London in pursuit of the best education for her children. But that is only half the story. Magdalen was very beautiful, sociable, clever, and depressive. George was devoted to her, and he was not the only one.

Drury cites three months in their house at Charing Cross, when she hosted 96 visitors, including politicians, poets, and the famous composer William Byrd. Among the poet-visitors was Donne, a generation older than George, but a devoted friend of his mother. Was Donne in love with her? It is not un- likely, given his regular visits, and the fact that she became a key muse and dedicatee of his work.

And it is equally hard to imagine young George not reading, and not being influenced by, the sheaves of poems by this older poet so treasured by his mother. As Drury explains, you cannot read much of Herbert's work without seeing the influence of Magdalen: "There's the Church as mother, the idea of mother-and-child as the ideal relationship, the idea that childhood means health. He was very mother-obsessed."

And, through Magdalen's devotion to her children, George was introduced to his great, abiding theme - love. Drury argues persuasively that "love" is the supreme value for Herbert, of greater value than the Church, than all of theology - greater value, even, than God. And this gives his poetry a lasting appeal for atheist and believer alike, since, as Drury puts it: "Love is everyone's ultimate and constant concern."

And he goes on to consider how, in Herbert's famous first line of "Love III" ("Love bade me welcome: yet my soul drew back"), "it would suffer if its first word were 'God' rather than love".

I ASK whether their shared vocation as Anglican priests was a particular bond between biographer and subject. "Being a priest doesn't obtrude much in his poetry," Drury says. "He's concerned with being a man facing the presence or absence of God."

But what about the tension - felt strongly by that other great priest-poet Gerard Manley Hopkins - between the callings of priest and poet, the pull between selflessness and self-absorption?

"His poetry is a way of sorting all that out. Herbert lived at a very anguished time to be a Christian. Post-Reformation. It had become a personal struggle, and he used the poetry to clear his mind, to seek that elusive 'something understood'."

But what about the impact of subject on biographer? Claire Tomalin has written about the particular strangeness of living "other people's lives", and Drury clearly agrees: "He became a voice in my head. But even then you never quite master all of his poems, because you keep reading them in new ways. His craftsmanship is absolutely amazing."

It is no surprise to learn that Drury is currently working on a new annotated edition of Herbert's poems, since there is so much brilliant textual analysis in Music at Midnight. But that prompts the question often asked of poets - should not the work stand by itself?

"The poems can stand alone," Drury re- plies, "but you understand more when you know something of the life."

And that makes sense of the book to me. More than most literary biographies, this one starts with the work, and moves out into the life. It is a method that Drury has used before, when working on religious paintings for the National Gallery: "I would take a Herbert poem, then read out from it into his life at the time.

"So, for example, his poem 'Dialogue' [a conversation between God and a human being] can be read in the light of the regular disputations he had to attend in Cam- bridge."

DRURY explains, in the chapter on Herbert at Cambridge, how these formal intellectual sparring sessions, when students were made to defend or attack a particular premise, left a lasting mark on Herbert. As the critic Helen Vendler points out, conversation in all its forms - argument, pleading, persuasion, intimate confiding - is the essential heart of Herbert's poetry, a craving for intimate friendship with God.

Herbert was, as Drury's book beautifully depicts, a mystic. He was never enslaved to theology, but longed for direct access to, and experience of, the God of love. If that makes him sound as "untouchable" as Weil, who famously shunned physical contact, and tried to live as pure a life of the mind and spirit as possible, then there is plenty of detail in Drury's account to complicate that view.

Mystic he may have been, but he was also fastidiously tidy, and was known at Cambridge as a dandyish dresser. He was a highly skilled lutenist who, Drury speculates, "would have liked to be a Dean, with a nice house and fine cathedral music".

He died a month short of his 40th birthday, probably of tuberculosis, having called for his lute the day before, and sung some of his poems to his wife and nieces.

I still love the Donne of "Death, be not proud", but, although Herbert's voice is quieter, and his struggles are shot through more with anguish than anger, his strange, rich, troubling music seems to me now more contemporary, more urgent, more unfathomable.

I will leave the last words to the late, great Seamus Heaney: "In the clear element of George Herbert's poetry is a true paradigm of the shape of things."

Michael Symmons Roberts is Professor of Poetry at Manchester Metropolitan University. His latest collection Drysalter (Cape, 2013) won the Forward Prize 2013.

Music at Midnight: The life and poetry of George Herbert, by John Drury, is published by Allen Lane. Ronald Blythe reviews it here.