When Amazon released its earnings last week, some were disappointed, but it was still clear that the Kindle has been doing pretty well. Amazon sold three times as many Kindle books in the first half of 2010 as it did in the first half of 2009, and it was recently revealed that Amazon is now selling more Kindle books than hardcover books.

"The Association of American Publishers’ latest data reports that e-book sales grew 163 percent in the month of May and 207 percent year-to-date through May," Amazon said. "Kindle book sales in May and year-to-date through May exceeded those growth rates."

The company also noted that five different authors have sold over 500,000 Kindle books. These include Charlaine Harris, Stieg Larsson, Stephenie Meyer, James Patterson, and Nora Roberts. James Patterson has sold 1.14 million e-books to date, 867,881 of which were Kindle books.

The company announced today that Larsson has now surpassed a million.

"Larsson’s books have captivated millions of readers around the world and ignited a voracious interest in the lives of its main characters Lisbeth Salander and Michael Blomqvist," said Russ Grandinetti, Vice President of Kindle Content. "It’s been exciting to have been a part of introducing so many people to these great books."

Amazon notes that the "Kindle Million Club" recognizes paid Kindle book sales. Free ones don’t count, so that says even more about Kindle book sales.