The Harry Potter books follow the lives and adventures of a young wizard and his friends, who all attend Hogwarts School of Witchcraft and Wizardry.
There are seven books in the series, and the final one, Harry Potter and the Deathly Hallows, was published in July 2007.
More than 11 million copies of The Deathly Hallows were sold on the first day it was in shops.
The basic themes in the books are magic, friendship, and good versus evil. Harry has to fight his arch rival, Lord Voldemort, in some way in all of the books.
The series has sold hundreds of millions of copies around the world and has been translated into more than 60 languages.
It's thought Potter creator and author JK Rowling has earned more than £500m from writing the books.