JungleScan is nifty service chronicled in Amazon Hacks that tracks over time the sales rank of many thousands of Amazon items. Add any item you want, and it will automatically go on the list. You can easily imagine that any author who knows about this service would be a regular, even neurotic, visitor to the JungleScan page for their book: “How am I doing today?”
Here’s an example. Benjamin Franklin is one of my heros. A few years ago I was looking for a good book about him, and I was surprised that there were no relative recent readable biographies of him. A few years passed, and BANG! now there are three, not to mention the superb recent PBS special. I conclude that I am either on the vanguard or stunningly average in my desires, depending on how you look at it. Anyway, two of the Franklin books are in the JungleScan database. Here is the chart for Edmund Morgan’s “Benjamin Franklin”, currently ranked at 7311. Here is Walter Isaacson’s book of the same title, now ranked at 22. Obviously Isaacson is giving Morgan a nasty spanking in the sales department, but it’s also interesting to look at the 90-day trendlines and try to guess at other dynamics going on. For instance, did the introduction of Isaacson’s book increase sales for Morgan’s? Maybe so.