Our photographer was out-and-about catching all the fun of the special day.
School pupils dressed up as everyone from Harry Potter and The Cat in the Hat, to Captain America and Spiderman - responding to the challenge to come to school as their favourite literary character.
And many of the teachers got involved too, making it a real day to remember.
Now in its 20th year, the day, which is designated by Unesco as a worldwide celebration of books and reading, is marked in more than 100 countries.
The main aim of World Book Day is to encourage children to explore the pleasures of books and reading by providing them with the opportunity to have a book of their own.
It has become one of the highlights of the school calendar, with children receiving a book token to buy a new book of their own.
In other countries it is celebrated on April 23 - William Shakespeare’s birthday.