Brand new stories from Neil Gaiman and Anthony Horowitz, the culmination of Gruffalo author Julia Donaldson\'s quest to find the UK\'s best storyteller and the country\'s biggest ever book show will all mark World Book Day tomorrow. Celebrated in over 100 countries around the world, World Book Day is the UK\'s largest festival of reading and aims to encourage a lifelong love of literature in children. Thousands of schools and nurseries are joining in, with more than 14m book vouchers given out to children, and hundreds of events – from Where\'s Wally \"flash mobs\" to author talks and literary fancy dress competitions – taking place up and down the country. Half a million children from around the world will watch authors including children\'s laureate Donaldson, Jacqueline Wilson and Artemis Fowl creator Eoin Colfer taking part in the online festival The Biggest Book Show on Earth on Thursday morning. Streamed live from London\'s Southbank Centre, the event will let children watch performances online as well as take part in an interactive question and answer session. \"I\'m so excited to be part of World Book Day\'s Biggest Show on Earth,\" said Donaldson. \"It\'s a fantastic way of bringing children together to meet some of the country\'s very best authors and illustrators. We can\'t wait to transport millions of children to exciting new worlds.\" Donaldson has also teamed up with How to Train Your Dragon author Cressida Cowell to find the country\'s best storyteller, with the parent, grandparent, sibling, schoolteacher or librarian they judge to be the most passionate reader to be announced tomorrow. Eight new books including the latest adventures of Winnie the Witch, a 25th anniversary edition of Where\'s Wally Now and the newest instalment of Derek Landy\'s Skulduggery Pleasant series will be free tomorrow with a £1 World Book Day token, while a free World Book Day app will see Malorie Blackman add to her popular Noughts and Crosses world in an exclusive new story. The app also features fresh material from Charlie Higson, Gaiman and Horowitz, who might have concluded the adventures of Alex Rider in his bestselling Scorpia Rising, but provides a glimpse back into the world of the teenage superspy in his specially penned new story. Lively discussions about \"if you could be a fictional character from any book for a day, who would you be?\" are already taking place on Twitter under the hashtag #fictionalforaday, prompted by the World Book Day Twitter account, with Lyra from Philip Pullman\'s His Dark Materials trilogy proving popular. Roald Dahl and Enid Blyton, meanwhile, were topping lists for the #growingupiread discussion, about favourite books read as a child. \"We can\'t wait to get the whole country sharing stories in time for World Book Day,\" said director Kirsten Grant. \"The £1 World Book Day Book Tokens are a great way to get young people of all ages started and there are some brilliant events lined up that will make this year\'s World Book Day bigger and better than ever before.\" Prime minister David Cameron has pledged his support for World Book Day, which he said \"plays an important role in helping children to develop a love of reading from an early age, supporting the inspirational work that takes place in schools and libraries up and down the country\". Citing Dr Seuss\'s The Lorax as his own favourite children\'s book, Cameron said that the books loved by children were \"something you treasure for the rest of your life\".