Pratchett gave up working for the CEGB to make his living through writing in 1987, after finishing the fourth Discworld novel, "Mort". His sales increased quickly and many of his books occupied top places on the best-seller list; he was the UK's best-selling author of the 1990s. According to "The Times", Pratchett was the top-selling and highest earning UK author in 1996. Some of his books have been published by Doubleday, another Transworld imprint. In the US, Pratchett is published by HarperCollins.