“USA TODAY collects sales data from booksellers representing a variety of outlets: bookstore chains, independent bookstores, mass merchandisers, and online retailers. Using that data, we determine the 150 top-selling titles of the week. The top 150 are published online Wednesdays at 6 a.m.
USA TODAY’s Best-selling Booklist reflects combined sales of titles in print and electronic format, if available. The rankings reflect sales from the previous Monday through Sunday.”
More info: https://www.usatoday.com/booklist