Previous threads had mentioned "In the Gravest Extreme" and "The Truth about Self Protection" by Massad Ayoob. These are great books, but quite old and sometimes hard to get.
"Lessons From Armed America" by Kathy Jackson is also a good book and has an Ayoob flavor since she hosts the MAG 40 class at the Firearms Academy of Seattle.
Yesterday a post on the TPI forum reminded me of Rory Miller and I noticed that Amazon has a lot of new paper and e-books by him.
I would like to recomment "Facing Violence – Preparing for the Unexpected". It covers a lot of the information that I got from attending the Massad Ayoob classes and for the Craig Douglas Managing Unknown Contacts discussion. It is reasonably priced in both paper and Kindle format and I think it would be very useful for you to read.