I don't know if this is possible given the constraints of Amazon, But if there is a way you could enable users to link their Amazon or other bookseller accounts tO SG as a way to easily identify which books a user has/need as well as which ones they are currently reading. In my head, this would also be an easy way to input Book data into the database. Of course, I understand this may be impossible right now but I just wanted to suggest it in case it is possible in the future.