TitleZ is a new free site (for now), It’s been in beta for years. You can track many books for free, and get some handsome graphs of their ranking. The good thing is that TitleZ will instantly give you the back history of a book’s ranking back to 2004. The downside of TitleZ is that you can’t export the data, or do much else.
A TitleZ track of my 1994 book, above. Below is a comparison chart of my two books in print.