Here we feature some of the many youngsters who have dressed up as colourful book characters for the day.
1. Magical day
Kai Skivington, nine, and Billie-Rae Skivington, six, as Harry Potter and Hermione Granger.
2. Blue is the colour
Archie, Freddie, Mia and Tallulah dressed as Smurfs.
3. Incredible Layla
Chelsea Louise Thomas's daughter Layla as Violet from the Incredibles.
4. Getting to the root of the matter
Lindsay Wishart sent this photo of Mollie, aged eight, as Miss Root from The Demon Dentist.