While researching the newly launched Carina Press epub, I came across this NovelRank website:
Amazon Book Sales Tracking This page shows a list of Carina Press titles sold in Kindle format on Amazon. If you click on a title, it will show the number of copies sold in June and July, as well as the date of the last sale and overall sales rank. Please keep in mind that Carina Press also sells ebooks on its website.
By choosing the 'Track Books' option and entering a title/author name you can look at other book sales. Apparently, if the book is not on the list, you can add it, so NovelRank would start tracking it.