The downloads are .zips so that the cyberpolice don’t break down my door, and within the .zips is an .epub of the book. You can view them on your computer with FBReader, or on an iOS device with Readmill. I’ve also linked the Goodreads page for each book so you can see whether or not the book is up your alley, and read what other people thought of it.
This is not necessarily a recommendation post because I haven’t yet read all of these, nor is it a comprehensive collection of every Borgia book out there: it’s just pretty much every Borgia ebook out there. Enjoy!