I get sent books for free by large publishers, for recommending to students, reading lists, and for my own personal enjoyment (!).
The topics aren't something I work on and so I don't use them, and the course is now finished. They also go out-of-date every year.
AIBU - or dishonest somehow? - in selling these on through Amazon (I am broke...)? Or is it simply my good fortune to have these which I can sell?