The Casual Vacancy has been knocked off its perch atop Amazon's bestseller list, falling to #2 behind Rick Riordan's The Mark of Athena. Riordan's book, which comes out October 2, has a 3.5 million-copy first printing in the U.S., while The Casual Vacancy has a 2 million-copy run. More astounding: social reads Website Goodreads tweeted on September 28 that The Casual Vacancy broke the record for all-time biggest "started reading" day for a book on Goodreads on September 27, the book's pub date. For The Mark of Athena, expect huge first week sales numbers as preorders alone will be great enough to make it one of 2012's biggest blockbusters: the book will have spent 148 days in Amazon's top 100 before even being published.