Lonely Planet is the largest travel guide book publisher in the world. The company is owned by American billionaire Brad Kelley's NC2 Media, which bought it in 2013 from BBC Worldwide for US$77 million (the equivalent of £45.5 million in May 2014) after it was valued at US$250 million in 2008. Originally called "Lonely Planet Publications", the company changed its name to "Lonely Planet" in July 2009 to reflect its broad travel industry coverage and an emphasis on digital products. After the Let's Go travel guide series that was founded in 1960, the Lonely Planet books were one of the first series of travel books aimed at backpackers and other low-cost travellers. As of 2011, the company had sold 120 million books since inception and in early 2014, it had sold around 11 million units of its travel apps. As of 2014, Lonely Planet's largest office is located in Footscray, a suburb of Melbourne, Australia, but its Franklin, Tennessee, United States (U.S.) office is the company's de facto headquarters. Other Lonely Planet offices are spread throughout the world, in locations such as London, United Kingdom (U.K.); Beijing, China; and Delhi, India.