This subcategory list is like a bestseller list for your niche. Amazon has 35 top-level categories (like Arts & Photography; Business & Investing) divided into dozens more subcategories. Unlike general bestseller lists compiled by the New York Times or USA Today, Amazon's subcategory lists show what people care about at the niche level, where passions run deepest.
Amazon's subcategories are discrete enough that just a few sales can push your title near the top, exposing your book to more people who care about that topic. In our example subcategory #Home & Garden > ... Organic#, your book could claim one of the top three spots with only two or three sales per week on Amazon.
Once you've bubbled up to the top of your subcategory, you're firmly inside the positive feedback loop. Amazon acts as a huge funnel, sending thousands of readers to your book. That's why some authors encourage their Web site visitors to buy books on Amazon--each additional sale boosts their exposure, prompting yet more sales.
"Simply put, the more customers you send to Amazon who buy your book, the more visible it will be on Amazon, and the more books Amazon will sell for you," says Morris Rosenthal, publisher of Foner Books.
If your book continues selling for six months or so, Amazon can assign it to more categories, making it even more likely browsers will find you after browsing in related categories. Books that sell moderately well eventually can be assigned to 12 or more categories, the same exposure as your book being shelved in a dozen different sections of a brick-and-mortar bookstore. The big difference is, Amazon is the world's largest bookstore.
To see your book's subcategory assignments on Amazon, find the section on your book's detail page headed #Look for similar items by category#. Clicking on those links takes you to a list of the subcategory's bestsellers.
Sometimes persistent publishers can talk the folks at Amazon into assigning their books to additional categories, or removing the book from inappropriate categories. Research other books in your niche, and see which categories they're displayed in.
Narrow a list down to 10 categories and send your list, ISBN, and contact information to Amazon. You can send your message, along with any other typographical corrections for Amazon, by using this form: