Of the many fine English-language writers to have emerged from India over the past 20 years, Amitav Ghosh is perhaps the most international. He has written about Bangladesh, Burma, Egypt, Cambodia, Britain and America, and his interest in those places where different cultures meet now finds its most exuberant expression in a hugely entertaining novel.

The first volume of a projected trilogy, Sea of Poppies is set in India in 1838. The East India Company, yet to be curbed of its wilder excesses by the British Crown, is amassing unimaginable wealth by growing opium and illegally exporting it to China. Peasant farmers have been obliged to turn over their fields to opium production, and this causes widespread poverty and hunger because “lands that had once provided sustenance were now swamped with the rising tide of poppies”. Furthermore, the Chinese are determined to stop a trade that is rapidly undermining the economy by turning millions of them into addicts.

A large cast of characters assembles in Calcutta, a teeming city in which numerous races and people of differing faiths and creeds live together. In dry dock, the Ibis, a former slave ship, is being refitted to take a large group of girmitiyas or “indentured migrants” to Mauritius. The Ibis has a British captain and first mate, an American second mate, Indian troops to maintain order, and a crew of Lascars; among its passengers are people of all nationalities, backgrounds and beliefs, some crossing the seas to escape difficulties at home, some being transported as convicts.

Both Calcutta and the Ibis are polyglot communities, and Ghosh revels in the energetic multilingual way his British, American, Indian, French and Lascari characters express themselves. He has ransacked not only Hobson-Jobson, the celebrated 19th-century dictionary of colloquial Anglo-Indian words and phrases, but also a more obscure 1811 English and Hindostanee Naval Dictionary of Technical Terms and Sea Phrases. The result is a glorious babel of a novel in which people speak everything from pidgin and Bhojpuri to the comically mangled English of a Bengali babu and a young Frenchwoman. Not that the British are always comprehensible: “Instead of the tottee-connah, off you’d go to a little hidden cumra, there to puckrow your dashy.” Carried along by the sheer energy of the narrative, most readers will soon tune in to this marvellously inventive lingo, but Ghosh has also provided an online tongue-in-cheek glossary, supposedly compiled by one of his characters.

In a novel where people often rely upon disguise or are not as they appear, language both obscures and reveals identities. Connected with this is a serious underlying theme about how we judge by appearances but are, in fact, little different under the skin. The pale offspring of a quadroon slave and her white master, the Ibis’s second mate, Zachary Reid, is officially “black” but can pass himself off as a Yankee gentleman, only to be despised by the first mate as a “tofficky young tulip”. Zachary’s love interest, Paulette, is French, but was raised alongside the son of her Muslim wet nurse whom she regards as her brother, and she can pass herself off as a coolie. Shared experience reveals as many similarities as differences, and the girmitiyas put aside their religious and social divisions aboard the Ibis, declaring themselves boat brothers. In the on-board chokey, meanwhile, a bankrupt rajah, who has been brought up in the utmost Bengali refinement, finds brotherhood with a filth-encrusted opium addict who is the illegitimate offspring of a Parsi and a Chinese woman. A Bengali accountant who feels imbued by the spirit of a holy woman and starts to hover somewhere between the genders feels that he “has become the key that could unlock the cages that imprison everyone, all these beings who were ensnared by the illusory differences of the world”.

Sea of Poppies boasts a varied collection of characters to love and hate, and provides wonderfully detailed descriptions of opium production, the perils of 19th-century seafaring, and life in 1830s Calcutta. It is utterly involving and piles on the tension until the very last page, which leaves the reader cast adrift along with some of the characters. The next volume cannot come too soon.

Sea of Poppies, by Amitav Ghosh

J Murray £18.99 pp471

Buy from BooksFirst for £17.09

Times Recommends

• Superfreakonomics by Steven D Levitt and Stephen J Dubner
• The Times picks the 50 best paperbacks of 2009
• Vincent van Gogh’s letters show the soul of the artist