Palm leaves sprout from the pillars of the British Library's basement galleries. Cupolas pop up from amid a maze of palace walls. And as the visitor steps into the display space, he feels reality vanishing. He is at the start of a journey that will lead him into a more exotic place.

The Ramayana is an ancient Sanskrit epic that tells the timehonoured tale of the battle between good and evil. It is the story of Prince Rama, who, with his loyal army of monkeys, sets out on a mission to rescue his beloved wife Sita from the clutches of a kidnapper, the demon king Lanka.

It is a tale that lies at the heart of Indian culture. First told as long ago as 500BC, it was endlessly tampered with over the ensuing millennium until, with elaborate back-stories added, cosmic dimensions included, long digressions inserted and local adaptations made, it eventually started to settle into its present form of an enormously long poem of some 24,000 verses, divided into seven books. It is to the East what the Iliad is to the West.

Wander around the perimeters of this exhibition and you will find displays of objects that, as well as evoking the poem's long history, also indicate how widely its influences spread. It was disseminated in a multiplicity of local versions throughout the Hindu and Buddhist kingdoms of South-East Asia - carved on temple walls in Java, adopted in Thailand and written down in Malay.

Its story is still vibrant, as objects that vary from ancient Sanskrit inscriptions through textiles and sculpture to the most garish contemporary kitsch make clear. The Kathakali dancers of Kerala still stamp out its rhythms in their flamboyant costumes. Shadow puppets still bring its battles to crepuscular life. It furnishes pictures for playing cards, patterns for carpets and story plots for Bollywood movie directors. This is a tradition that is very far from dead, as an Indian television serialisation in the late Eighties proved. More than 100 million aficionados would stop whatever they were doing, pitching passengers from rickshaws and shutting up shop, to watch the programme.

Visitors to The Ramayana: Love and Valour in India's Great Epic will easily find themselves slipping into its entrancing grip. But unless you have inordinate amounts of time - and you will need it if you are to begin to appreciate properly each of the 130 manuscript pages - I wouldn't spend too much time with the peripheral objects. Focus on the manuscript. It is magnificent.

Commissioned by the ruler of Mewar in southern Rajasthan between 1649 and 1653, it takes more than 400 paintings to tell the entire story of the Ramayana in the most scrupulous pictorial detail. It is widely considered to be among the greatest of 17th-century Indian manuscripts, but, presented as a gift to an Englishman, has been bundled away in a series of huge bound volumes in the British Library since 1844.

This is the first time that the public will have the opportunity to admire it - and probably the last for some years. Recently unbound from the volumes that protected them, an extensive selection of the newly mounted but fragile paintings unspool like some exquisitely sophisticated cartoon strip along the walls.

At first glance the images that crowd the little jewel-bright oblongs - the rectangular shape reflects that of the palm leaves on which the Ramayana would originally have been recorded - can look pretty bewildering. But they are beguilingly exotic. You are in a land of elephants and cobras, banyans and camels, where tigers leap from rock crevices and crocodiles prickle rivers, where yogis perform the most excruciating contortions, giants snack on water buffalo and to give birth to a blue baby is not at all worrying. It is a sign that the child is an incarnate god.

But you might do well to bring your own magnifying glass. As you peer into pages in which, for instance, the entire panoply of a royal court can crowd the picture, the gaze becomes perplexed by the proliferation of minute detail. The craftsmanship is exquisite. Using the mineral pigments that so often reflect the rich terra cottas and burnt umbers of the Rajasthan landscape, artists pick out each detail with their squirrel-hair brushes. Everything is noticed: the glow of each pearl, the wink of each ruby, the embroidery on each veil and the pattern on each sari. From twinkling crown to embroidered slippers, from jewel fringed veil to lacquered toenail, nothing is missed. No wonder historians turn to this rare survival when they want to find a picture of life in the 17th-century Indian court.

This commission was a vast project. It involved several studios over which different masters presided like cinematic directors. The most astonishing talent is undoubtedly that of Sahab Din, who, rather than concentrating on representing a single narrative event in each frame (as the Persian Moguls of the time would have done), revives an ancient Indian tradition of simultaneous narration in which each picture can represent several episodes of the story and portray the same character several times over. This, along with a pioneering use of bird's-eye perspective, allows him to give every detail of the story pictorial representation.

Using walls or doorways or trees or rocks to divide up the scenes and create a sense of spatial and temporal progression, he spreads out the story like a rug. The spectator - with the help of accompanying texts or the clear and beautifully illustrated catalogue - soon learns to read its eloquent patterns. Look at the image, for instance, in which an exiled Rama is first told of the death of his father. The story, from the smelling of the heads of the two brothers who bring the news, through the descent to the river of a grief-stricken Rama, who performs ritual offerings pouring water on mats of grass, to the re-ascent to sit grieving outside the hut, is told in a sequence that runs anti-clockwise round a hill. Sahab Din captures all the complexities with pictorial grace.

Other styles are more immediate. Artists work in a rougher, more dramatic way, whipping up a witch's dust-storm, for instance, that sets you blinking the sand from your eyes, or sending a slaughtered ogre toppling in great butchered chunks like a building tumbled by an earthquake. This style has an appealing directness that can often be very funny, as when a series of Lilliputian figures busy themselves trying to wake a snoring giant, delivering great bonging blows to his belly, bawling into his ear and prodding him with tridents, while a pile of bloody snacks are prepared for his breakfast.

But in the long run it is the subtleties of the master Sahab Din that will probably hold your attention - not least as he refines and masters his art as the commission progresses, heightening the dramatic impact of a scene, as when a herd of elephants plunges into the Ganges, by having no horizon line and thus enclosing a sense of tumultuous energy. It is a method he refines, using it to capture the claustrophobic hysteria of an angry king or the interlocking energy of the arm-whirling, rock-hurling, branch-bashing battles.

It is through the use of such skills that the artist inveigles the imagination. The spectator gets swept into the drama, marching (right to left across the page) to exile with Rama and then, dozens and dozens of images later, marching back (left to right) again. The adventures in between are rich and varied, sometimes sad, sometimes tender, often ravishingly beautiful and sometimes luridly violent. They feel rare and strange. And yet, as you are drawn ever deeper into the spirit of the piece, you feel the fundamental stirrings of an emotional response. It is this that gives the Ramayana its universal appeal.

The Ramayana: Love and Valour in India's Great Epic is at the Pearson Gallery, British Library, NW1 (01937 546060), until Sept 14

THREE MORE MUST-SEE ILLUSTRATED MANUSCRIPTS AT THE BRITISH LIBRARY

The Lindisfarne Gospels Witness one of the great moments of artistic awakening in our country. Enter the spiritual realm of 7th-century monks illuminating the stories of their faith with astonishing labyrinthine patterns.

The Golden Haggadah This sumptuously illuminated book, produced in about 1430 in Northern Spain and used in Jewish households on the eve of Passover, glows with an almost mystic light.

Sultan Baybar's Qu'ran Handwritten in gold for the court of a 14th-century Sultan, this is one of the most magnificent Islamic manuscripts in the world.

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