A best-selling Indian author has won a $1 million advance for the South Asian rights to a new trilogy, the biggest such deal ever struck, his publishers said on Monday. India's Westland Press has paid 50 million rupees to Amish Tripathi, a banker-turned-writer, as an advance for the South Asian rights to his next series of three books. "The offer was made on the basis of not only the past sales record but also in our belief in Tripathi as a writer and his ability to deliver another blockbuster trilogy," Gautam Padmanabhan, chief executive of Westland, told AFP. Tripathi saw half a million copies of his recent mythological fantasy "The Oath of the Vayuputras" -- the final book of his last trilogy --- fly off the shelves within a day of its release last week, local media reported. Other acclaimed Indian writers, such as Vikram Seth and Amitav Ghosh, have garnered bigger advances in the past but their deals have included rights for countries such as Britain and the United States. "The advance we have paid is the largest by an Indian publisher for South Asian rights alone," Padmanabhan said. Padmanabhan said the deal has given Westland, part of the tea-to-steel Tata conglomerate, access to Tripathi's "pool of various plot ideas". Tripathi's trilogy is based on the premise that the Hindu gods were not mythical beings but creatures of flesh and blood. It has notched up gross retail sales of $4 million since the first book was published in 2010. The deal was welcomed by the publishing industry in a country which has increasingly become a lucrative market for English-language books. "The success of his books is empowering for other Indian authors. They need to create their own success story and the deals will follow," Shobit Arya, founder of Wisdom Tree, another publishing house, told AFP. "Even for Tripathi, money followed success, and not the other way round."