Although it’s been available for merely less than a week, Rick Riordan’s The Mark of Athena has already knocked J.K. Rowling’s The Casual Vacancy off the top of Amazon’s Best Sellers list.

Remarkably, Athena has spent nearly five months in the Amazon Top 100. It is the third book in the Heroes of Olympus series. Fifty Shades held the top spot on Amazon’s Best Sellers list for months despite competition from big name authors, so it’s surprising to us to see Rowling leave after only a week.

Rowling’s quick departure from the top spot may be due to the fact that the book had racked up an impressive one million pre-orders prior to the September 27 release, so sales didn’t stay strong online for long. Word of mouth may also be affecting Rowling’s strength; the book has been met with critical reviews from readers who see the book as a majorly obscure departure for the beloved author.

It’s not all bad news for The Casual Vacancy. It set a Goodreads record after being marked “now reading” on the site by more people in one day than for any book in the site’s history.

You can read our Casual Vacancy review in which we are generally positive about the book and definitely do not view it as a book for younger readers. Speaking of younger readers, parents should check out our parental guide to help decide if the book is good for their “darlings.”

This news was first noted by Publisher’s Weekly. Do you have any guesses as to why Rowling left the top spot so quickly?