Kahlil Gibran is said to be one of the world's bestselling poets, and his life has inspired a play touring the UK and the Middle East. But many critics have been lukewarm about his merits. Why, then, has his seminal work, The Prophet, struck such a chord with generations of readers?

Since it was published in 1923, The Prophet has never been out of print. The perennial classic has been translated into more than 50 languages and is a staple on international best-seller lists. It is thought to have sold tens of millions of copies.

Although practically ignored by the literary establishment in the West, lines from the book have inspired song lyrics, political speeches and have been read out at weddings and funerals all around the world.

"It serves various occasions or big moments in one's life so it tends to be a book that is often gifted to a lover, or for a birth, or death. That is why it has spread so widely, and by word of mouth," says Dr Mohamed Salah Omri, lecturer in Modern Arabic literature at Oxford University.

The Beatles, John F Kennedy and Indira Gandhi are among those who have been influenced by its words.

"This book has a way of speaking to people at different stages in their lives. It has this magical quality, the more you read it the more you come to understand the words," says Reverend Laurie Sue, an interfaith minister in New York who has conducted hundreds of weddings with readings from The Prophet.

"But it is not filled with any kind of dogma, it is available to anyone whether they are Jewish or Christian or Muslim."

The book is made up of 26 prose poems, delivered as sermons by a wise man called Al Mustapha. He is about to set sail for his homeland after 12 years in exile on a fictional island when the people of the island ask him to share his wisdom on the big questions of life: love, family, work and death.

Its popularity peaked in the 1930s and again in the 1960s when it became the bible of the counter culture.

The Prophet On marriage: "Love one another but make not a bond of love: Let it rather be a moving sea between the shores of your souls. Fill each other's cup but drink not from one cup." On children: ''Your children are not your children. They are the sons and daughters of Life's longing for itself.'' On beauty: ''Beauty is eternity gazing at itself in a mirror. But you are eternity and you are the mirror.''

"Many people turned away from the establishment of the Church to Gibran," says Professor Juan Cole, historian of the Middle East at the University of Michigan who has translated several of Gibran's works from Arabic.

"He offered a dogma-free universal spiritualism as opposed to orthodox religion, and his vision of the spiritual was not moralistic. In fact, he urged people to be non-judgmental."

Despite the immense popularity of his writing, or perhaps because of it, The Prophet was panned by many critics in the West who thought it simplistic, naive and lacking in substance.

"In the West, he was not added to the canon of English literature," says Cole. "Even though his major works were in English after 1918, and though he is one of bestselling poets in American history, he was disdained by English professors."

Image caption Gibran sketched the Prophet after a dream

"He was looked down upon as, frankly, a 'bubblehead' by Western academics, because he appealed to the masses. I think he has been misunderstood in the West. He is certainly not a bubblehead, in fact his writings in Arabic are in a very sophisticated style.

"There is no doubt he deserves a place in the Western canon. It is strange to teach English literature and ignore a literary phenomenon."

Gibran was a painter as well as a writer by training and was schooled in the symbolist tradition in Paris in 1908. He mixed with the intellectual elite of his time, including figures such as WB Yeats, Carl Jung and August Rodin, all of whom he met and painted.

Symbolists such as Rodin and the English poet and artist William Blake, who was a big influence on Gibran, favoured romance over realism and it was a movement that was already passe in the 1920s as modernists such as TS Eliot and Ezra Pound were gaining popularity.

He painted more than 700 pictures, watercolours and drawings but because most of his paintings were shipped back to Lebanon after his death, they have been overlooked in the West.

Professor Suheil Bushrui, who holds the Kahlil Gibran chair for Values and Peace at the University of Maryland, compares Gibran to the English Romantics such as Shelley and Blake, and he says that like Gibran, Blake was dismissed in his own time.

"He was called 'mad Blake'. He is now a major figure in English literature. So the fact that a writer is not taken seriously by the critics is no indication of the value of the work".

In Lebanon, where he was born, he is still celebrated as a literary hero.

His style, which broke away from the classical school, pioneered a new Romantic movement in Arabic literature of poetic prose.

A poet's life Born to Maronite Catholic family in Lebanon, 1883

Moves to US aged 12 with mother and siblings after father imprisoned for embezzlement

Settles in South Boston's Lebanese community

Clerical error at school registers his name as Kahlil, not Khalil

He was a talented pupil and came to the attention of local artist and photographer Fred Holland Day

Returns to Lebanon at 15 to study Arabic

Soon after, he lost his mother, sister and brother to TB and cancer within months of each other

Back in the US in 1904, he meets Mary Haskell

In 1908, goes to Paris for two years to study art in the symbolist school

First book of poetry published in 1918, then The Prophet five years later

Dies in 1931 from cirrhosis of the liver and TB

Inspires a play Rest Upon the Wind, which tours UK and Middle East in 2012

"We are talking about a renaissance in modern Arabic literature and this renaissance had at its foundation Gibran's writings," says Professor Suheil Bushrui, who holds the Kahlil Gibran Chair for Values and Peace at the University of Maryland.

In the Arab world, Gibran is regarded as a rebel, both in a literary and political sense. He emigrated to the US at 12 but returned to study in Lebanon three years later where he witnessed injustices suffered by peasants at the hands of their Ottoman rulers.

"He was a Christian but he saw things being done in the name of Christianity which he could not accept," says Bushrui.

In his writing, he raged against the oppression of women and the tyranny of the Church and called for freedom from Ottoman rule.

"What he was doing was revolutionary and there were protests against it in the Arab world," says Juan Cole. "So he is viewed in Arabic literature as an innovator, not dissimilar to someone like WB Yeats in the West."

Image caption Gibran the painter created more than 700 works, including this one of his family

Political leaders considered his thoughts poisonous to young people and one of his books, Spirit Rebellious, was burnt in the market place in Beirut soon after it was published.

By the 1930s, Gibran had become a prominent and charismatic figure within the Lebanese community and New York literary circles.

But the success of his writing in English owes much to a woman called Mary Haskell, a progressive Boston school headmistress who became his patron and confidante as well as his editor.

Haskell supported him financially throughout his career until the publication of The Prophet in 1923.

Their relationship developed into a love affair and although Gibran proposed to her twice, they never married.

Haskell's conservative family at that time would never have accepted her marrying an immigrant, says Jean Gibran, who married Kahlil Gibran's godson and his namesake and dedicated five years to writing a biography of the writer.

In their book, Jean Gibran and her late husband didn't shy away from the less favourable aspects of the Gibran's character. He was, they admit, known to cultivate his own celebrity.

He even went so far as to create a mythology around himself and made pretensions to a noble lineage.

But Jean Gibran says that he never claimed to be a saint or prophet. "As a poor but proud immigrant amongst Boston's elite, he didn't want people to look down on him. He was a fragile human being and aware of his own weaknesses."

But arguably for Gibran's English readers, none of this mattered much.

"I don't know how many people who picked up The Prophet, read it or gifted it, would actually know about Gibran the man or even want to know," says Dr Mohamed Salah Omri.

"Part of the appeal is perhaps that this book could have been written by anybody and that is what we do with scripture. It just is."