It seems to be much better than Jungle was. They even offer some FAQ that include a bit of insight to the meaning behind the Amazon sales rank ranges. So - for those folks that check their sales ranks like they're stock trading, enjoy!
Here's what they say:
So, what's a good sales rank for a book? What's not so good?
There is, of course, no hard and fast rule about what constitutes a best-seller, whether you are looking at sales ranks or actual sales volume. However, we'll throw caution to the wind and offer a few generalizations.
First, it's important to look at a book's average sales rank over time--a book that spikes to, say, number 25 on Amazon for an hour or two may be selling well for that brief period of time (perhaps because the author just appeared on a morning talk show or got a favorable review in a regional newspaper), but you'll want to see how that book performs over days or weeks to fairly judge its success. Plenty of books break into Amazon's top 1000 or even top 100 for a few hours but are not able to sustain the high ranking over time.
So, bearing the above very much in mind, here's a temperature gauge you can use to get an idea about a particular title's success. The following numbers apply to average sales ranks over time:
< 100 = Best-seller. Author, publisher, agent are all getting rich
101-1000 = Extremely good performer. Any publisher/author would be thrilled.
1001-10,000 = Very successful book. A few of these can sustain a small publishing company.
10,001-50,000 = A successful book by most industry standards.
50,001-100,000 = Not bad.
100,000 - 500,000 = Not good.
500,000+ = Poor.
Keep in mind that books with average ranks above 100,000 may have performed much better before TitleZ started tracking them. However, books that launch with ranks above 100,000 are probably not considered successful from a publishing industry point of view. Of course, the book could be selling well through non-bookstore channels such as trade shows, speaking events, etc. In general, though, we've found that Amazon sales ranks provides a good indicator for how a title is doing throughout the book market as a whole.