Rory Miller's books, David Grossman's, Gavin de Becker to name a few other authors, all have useful knowledge.
Coopers old book Principles of Personal Defense
... buy it.
That Amazon link will take you to other related books, most listed in the above posts.
As Ayoob points out, you really need to know your State's laws on the subject along with the fact that an attorney who knows the subject is going to be paramount in the event you actually use lethal force and how to deal with the aftermath. So maybe something from Alan Korwins group as well.
And just because... Sun Tzu, The Art of War
has age old wisdom worth taking to heart (he wrote a little while before firearm use became the norm