I find it suspicious that the sort by rating is identical to the sort by title. A bug, perhaps?
I am seeing a (slightly) different ordering of results
The most likely answer is that all those books have the same rating, so it's falling back to tie-breaking by title.
Do you rate books in your Library? Do you have Community Ratings enabled (to provide a default rating for books you haven't rated)?
That explains it - I confused ranking with rating when I expected a different order. I rarely rate books ... I need some negative values to give honest ratings. [:#]
