If you are going to pirate the book, you might as well just go straight to something like Pirates Bay. It's much easier.
Very many books are not available on torrent sites.
Very many are available on library genesis among others. The pirate bay is a bad place for books.
As mentioned just up thread, if you don't purchase in the most recent KFX DRM format, you can strip the DRM. However AFAIK this is illegal to do for Kindle Unlimited ebooks. You are not supposed to keep them, just borrow.