Terry Pratchett's final Discworld novel hits shelves tonight

Fans of the author Terry Pratchett are in for a treat tonight. The Discworld creator's last book, The Shepherd's Crown goes on sale, just a few months after the author's death from Alzheimers' last March. To mark the occasion, the UK bookseller Waterstones is opening it's store in London's Piccadilly at midnight. Avid readers are expected to queue round the block to get their hands on a hard copy of the novel. So what does this film-premier-style launch say about the state of the book industry in the era of the ebook reader? The CEO of Waterstones, James Daunt, has been talking to Marie Keyworth.