[Deskisamess]

I suspect there isn't a definite number of books that will tip a person past the limit. You can't really compare 10 books of 280 pages with 10 books of 10-40 pages.

The "limit" is most likely based on other algorithms.

Like the old example I posted...the very small books being borrowed may trigger red flags.

Editing to add...it may be "fraud" of the book sellers, not the subscriber that Amazon is concerned about. Unfortunately the customer is pulled in to the issue as well.