To understand what you are trying to do can you provide more info?
First of all I can’t change the entries to books instead of or addition to products
All listings will be products, only two fields help identify the product type, this is category and product type, which can be set to correctly identify what you sell. However I’m unsure what you are trying to do. Please provide more details.
and second of all I can’t route it to pick up information about my product ratings.
Yes, that sounds correct in terms of the product data feed. You will not be able to pull this data as Google does not accept it.
However, if you mean product review feed, then the app I think is limited to a few review platforms. The best option is to directly link it up to Google merchant center, to know if your review platform supports this, reach out to the support team.
The questions above, is for me to understand what you are trying to do. As I manage feeds day in and day out, I like to learn what people are trying to do.