Can't find books in finder

Hi,

Where do I find my Books library on Mac? I've looked in "Mobile Documents" and in the "Containers" folders but can't find any of the books I've downloaded from Safari and imported into Books. They show up and read fine in the app.

Also a separate but related question that someone might be able to answer... if I drag and drop an EPUB book from the Books app onto desktop, and then try drag and dropping to my kindle, it won't show up. Is this a DRM issue? This is only happening with books that I am drag and dropping from the Books app, not any of the EPUB books that have been downloaded in Safari.