If there's one thing authors obsess about most it's sales figures for their books. This is often reflected in an addictive urge to check the Amazon sales rank - but that's only a substitute for the real thing. We want to know how many books are selling.
Publishers typically have a lot of information about sales, but rarely share it with the author in detail, except every six months or so in the royalty statement. But thanks to a service called Book Scan, the data is out there on a weekly basis for most (though admittedly not all) retail outlets. And we're not talking orders, which can always be returned, but hard sales through the till.
Amazingly Amazon now makes this available to authors with books published in the US. It's only paper books, not ebooks, but includes both Amazon and plenty of outlets. You can look back over 8 weeks data, broken down to the main selling books, a display that can either be uplifting or depressing, depending on the way the bars are going. The bar chart shown, by the way, is my sales for the last 8 weeks. You can either look on it that things are going rather well, or that they were rubbish 8 weeks ago. (The actual chart includes totals, and you can hover the mouse to see how many books are in each part of the bar.)
This is fascinating information - if you are published in the US and aren't on Amazon's Author Central service which provides this data, run don't walk to your computer.
Now I just have to wait to see if that slight fall was just a random variation or could be the start of a trend. Once more with the feeling. The only way is up...