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NEW YORK (CNN) — Harper Lee's "Go Set a Watchman" may have been Goodreads' best fiction book of 2015.

Ta-Nehisi Coates' "Between the World and Me" may have dominated honors given to the year's literary output.

But when it comes down to what sold the most copies on Amazon.com — the country's biggest online bookseller — the winner is Paula Hawkins' "The Girl on the Train."

Amazon put out its list of 2015's best-sellers today, and the selection was an intriguing mix of history, potboilers and mystery, with Hawkins' debut novel — about an alcoholic woman struggling to remember a possible crime — at No. 1.

Second on Amazon's list is E.L. James' version of "Fifty Shades of Grey" as told from Christian Grey's point of view, "Grey."

Lee's controversial "Watchman," an early draft of what became "To Kill a Mockingbird," was No. 3. However, it was the best-selling print book, while Hawkins' tome led Kindle downloads.

Veteran best-selling authors also had their places in the top 20. David Baldacci, Lee Child, John Grisham and Nora Roberts all made Amazon's list, as did Erik Larson and David McCullough, writers of the top 20's only nonfiction works, "Dead Wake" and "The Wright Brothers," respectively.

Notably, two coloring books made the top 20, a sign that the trend hasn't flagged.