Originally Posted by HarryT
How valid an assumption is that? I would have thought that there would be a very large number of books which might appear in multiple categories, in which case the total count might be considerably inflated!
I assumed the same as you have. So I checked a handful of titles to see if I could find them in multiple categories. For example, I looked for Bill Clinton's book "My Life" (which appears in Biographies) in other likely categories (Politics and Government, Mysteries and Thrillers, Romance, Horror, Science Fiction) and couldn't find it. (Okay, just having a little fun.
) I was suprised to find no books in multiple categories and I've repeated those tests several times since. I can't say that there aren't some double or triple counts but it would appear that there aren't many. Also, if you search on the letter "a" (presumably which would have to appear alone in the title, author's name, or description to generate a hit), you get 26,931 hits compared to 30,154 from the sum of the categories. So I'm pretty comfortable that their current total is about 30,000. Frankly, I couldn't care less whether it's 25,000 or 35,000. I'm really looking for big trends.