I've had a behind-the-scenes resource for years to track book sales, and I get monthly royalty statements from my publisher, Virtual Bookworm. But many clients wait 6 months or more to know what their book is doing in the market.
Now, Amazon lets you see this information for your own books, in your Amazon Author Central pages. If you don't have an Author Central page at Amazon yet, better get going...
Then follow this link, sign in and track your weekly sales. https://authorcentral.amazon.com/gp/metrics
Thanks for the early Christmas present, Amazon !!