J.K. Rowling’s Harry Potter series is known by everyone and loved by many but one installment of the series stands out above the others for its popularity.

The first novel in the series, Harry Potter and the Philosopher's Stone, has sold in excess of 120 million copies, making it one of the bestselling books in history. 

The Harry Potter brand has been estimated to be worth as much as £19.34 billion.

Rowling’s books have sold more than 600 million copies worldwide, making them the best-selling book series in history.

The last four books all set records as the fastest-selling books ever, with the final installment selling roughly 2.7 million copies in the United Kingdom and 8.3 million copies in the United States within twenty-four hours of its release.

Harry Potter became increasingly popular after the films were made, adding value to the franchise.

Surprisingly, twelve publishers had rejected the first Harry Potter book, Philosopher's Stone, until Bloomsbury decided to pick it up.

Deathly Hallows broke its pre-order record, with more than 500,000 copies pre-ordered through Barnes & Noble. 

This record statistic was broken by Harry Potter and the Order of the Phoenix, with 8.5 million copies sold, which was then shattered by Half-Blood Prince which sold 10.8 million copies.

Rowling’s series has established itself as one of the most successful fictional works of all time, with an incredible amount of sales.

The most successful books of the series are:

• Harry Potter and the Philosopher's Stone - 120 million

• Harry Potter and the Chamber of Secrets - 77 million

• Harry Potter and the Prisoner of Azkaban - 65 million

• Harry Potter and the Goblet of Fire - 65 million

• Harry Potter and the Order of the Phoenix - 65 million

• Harry Potter and the Half-Blood Prince - 65 million

• Harry Potter and the Deathly Hallows - 65 million