1983. The paperback edition was published by Corgi, an imprint of Transworld, in 1985. Pratchett's popularity increased when the BBC's Woman's Hour broadcast The Colour of Magic as a serial in six parts, and later Equal Rites. Subsequently, the hardback rights were taken by the publishing house Victor Gollancz Ltd, which remained Pratchett's publisher until 1997, Colin Smythe having become Pratchett's agent. Pratchett was the first fantasy author published by Gollancz. 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. According to the Bookseller's Pocket Yearbook (2005), in 2003 Pratchett's UK sales amounted to 3.4% of the fiction market by hardback sales and 3.8% by value, putting him in second place behind J. K. Rowling (6% and 5.6%, respectively), while in the paperback sales list Pratchett came 5th with 1.2% and 1.3% by value (behind James Patterson (1.9% and 1.7%), Alexander McCall Smith, John Grisham, and J. R. R. Tolkien). He has UK sales of more than 2.5 million copies a year. His 2011 Discworld novel Snuff became the third-fastest-selling hardback adult-readership novel since records began in the UK, selling 55,000 copies in the first three days. Alzheimer's disease In August 2007, Pratchett was misdiagnosed as having had a minor stroke a few years before, which doctors believed had damaged the right side of his brain. In December 2007, he announced that he had been newly diagnosed with early-onset Alzheimer's disease, which had been responsible for the "stroke". He had a rare form of posterior cortical atrophy (PCA), a disease in which areas at the back of the brain begin to shrink and shrivel. Describing the diagnosis as an "embuggerance" in a radio interview, Pratchett appealed to people to "keep things cheerful" and proclaimed that "we are taking it fairly philosophically down here and possibly with a mild optimism." He stated he felt he had time for "at least a few more books yet", and added that while he understood the impulse to ask "is there anything