NEW YORK -- It's good news for novelist Veronica Roth: "Divergent" is a hit at the box office and a blockbuster at book stores.

A spokeswoman for HarperCollins Children's Books said Tuesday that the young adult series set in a dystopian future has been selling 500,000 copies a week over the past three weeks.

The movie "Divergent" is based on the first book and stars Shailene Woodley, Theo James and Kate Winslet. The action-thriller was released March 21 and has already made nearly $100 million.

The first "Divergent" book was published in 2011, and total sales for the series now exceed 18 million copies. As of Tuesday afternoon, four of the top 10 sellers on Amazon.com were "Divergent" books.