A salient point stands out from all the above comments:

… if you can use it to make people read more, it is wonderful …

."A book which people praise and don't read."…

...But I would like to know why so many people buy books on a talk-show host's say so…

So they’re buying, but are they reading? I suppose that if only 1% actually read who otherwise would not, that is a worthwhile gain.

The lending library figures for the same works loaned out to new members over the same period would be interesting, but I doubt if those statistics are extracted from the records.