Can I load books into BAM Reader that I have purchased elsewhere?

Yes. If the eBooks you've purchased use Adobe DRM or are DRM-free, you have the ability to side load them into BAM Reader. You will need to authorize BAM Reader with the same Adobe ID that you used to authorize your other computer or device in order to read Adobe DRM eBooks on BAM Reader.

Can I read books in BAM Reader that I have purchased for the Nook?

Yes