Differences among lists
Bestseller lists may vary widely, depending on the method used for calculating sales. The Book Sense bestseller lists, for example, use only sales numbers, provided by independently owned (non-chain) bookstores, while the New York Times list includes both wholesale and retail sales from a variety of sources. A book that sells well in gift shops and grocery stores may hit a New York Times list without ever appearing on a Book Sense list. USA Today has only one list, not separated into fiction/non-fiction and hardcover/paperback, so that relative sales among these categories can be ascertained.
Lists from Amazon.com, the dominant on-line book retailer, are based only on sales from their own Web site, and are updated on an hourly basis...
click the link above to read the full article