If you sell your own book, you know exactly how many books you printed, how many have been sold (through your online shopping cart), and how many are left to be sold in the printing.
Oddly enough, when books are published by traditional publishers and go through the bookstore system, there are very few avenues open for authors and even publishers to track "real" sales of books. The Bookscan report from Neilsen Broadcast Data Systems, available since 2001, provides weekly sales by the major book retailers. But only the very largest companies can afford this expensive service.
It is virtually impossible to estimate the real sales of a book from the quantities that are shipped to the stores. Remember, all "sales” to bookstores are made with a long-established, full-price return policy anytime. That means all the books could be returned to you, even a year later. Major publishers expect overall return rates of 20 percent to 30 percent, but individual books can be much, much higher.
When your book is returned, it doesn’t mean that someone bought it, didn’t like it, and sent it back through the bookstore. Far more likely, it was never sold in the first place, and the bookstore returned it to the distributor after sixty to ninety days.
You will see sales numbers on your royalty statement, but generally there is also a reserve for expected returns as well. If your book is published by a traditional publisher or printed by Lightning Source, you can call the distributor Ingram’s sales tracking phone number, 615-213-6803, to hear about sales for both the previous week and last year.
It seems that all authors these days say their book is a best seller, and that’s because there is no established, objective criteria for what that means. There are roughly forty national and regional best-seller lists in the United States. The New York Times’ list is probably the most well known and respected. Another one that is well known, especially inside the publishing industry, is provided by Publishers Weekly (PW). In 2005, 442 adult titles were declared best sellers, according to the Publisher’s Weekly compilations.
Some best-seller lists such as those belonging to Publisher’s Weekly and USA Today are based on national surveys, with others on much less objective criteria. The New York Times bases their list on a poll of both chain and independent bookstores. The list from the American Booksellers Association polls only independent bookstores. The Los Angeles Times polls thirty bookstores in the metropolitan area to compile its list.
Only eight self-published books have made it to number one on the Publishers Weekly best-seller list.