The e-book business is thriving, despite the competition between digital, print and audible books, according to the boss of an e-reader company. The publishing sector has been experiencing recovery in recent years, after a period of decline . Between 2011 and 2014, publishing revenue fell from US$165 billion to US$145 billion, according to statistics from Euromonitor. The global book market shrunk 7.4 per cent between 2011 and 2012. But the industry has proven to be resilient, according to Michael Tamblyn, CEO of Kobo, which sells e-reader apps and devices, as well as e-books. "I think what's amazing about this industry is every year it finds a new driver for growth and so we see that in the move back and forth between print and digital," says Tamblyn. According to Tamblyn, the industry's most valuable customers, those who buy several books a month, are reading both print books and digital e-books, rather than one or the other. "Those people who are buying the most have allowed those two things to co-exist," he said. "We are seeing the two formats kind of living together, rather than one supplanting the other." However, the e-book market is facing some headwinds. Sales of e-books were down 12.7 per cent between January and November 2015 compared to the year before, according to statistics released last month from the Association of American Publishers (AAP). Meanwhile, audio books are growing in popularity. Sales rose by 40.3 per cent in 2015, according to the AAP. One audio book company, Audible, said it was experiencing significant growth. "Audible membership growth is consistent at 40 per cent year on year, as more consumers realize how well audiobooks can fit into their busy lives," according to Tracey Markham, country manager for Audible. "When it comes to new members, two thirds of our new members are first-time audiobook buyers and we're confident that our rich and varied library will keep them coming back for more." Tamblyn also discussed the increasing success of self-published books on the market. Last year, 22 per cent of e-books sold in the U.K. were self-published, according to Nielsen Book UK. "Agents and publishers still dominate the market but self-published has become a real, viable channel," Tamblyn said. "More often than not the customer who's buying this doesn't necessarily know they are buying a self-published book. They are so well produced, so well edited, so well designed that they just sit on the shelf with everything else."