No particular order:

Battle of Britain by Quentin Reynolds - was my dads favorite book growing up and read it constantly when I was younger.

Mossflower By Brian Jacques - helped really kick my love of reading in to the next gear by finding the fantasy genre, still remember where I was when my dad bought me the book. Can't thank the owner or manager who recommended it enough. me with a love of reading at a young age.

Malazan Book of the Fallen: Taking liberty by including this entire series, but it is called the "book" of the fallen. I come back to this all the time and confirmed my thoughts that fantasy / sci fi has tons to offer in literature despite some people's belief. Also has helped me really dive in and analyze the writing craft in books I read.

Old Wine New Wineskins by my grandmother: I helped her edit and put out a second edition of this book, her take on history and its timeline. In addition to that connection, it also inspired me that writing a book was achievable - working on it very slowly, but I know it is possible.

I'm going to think about #5 a bit, lots could go here.

Also, to answer your question - I would recommend looking in to Ordinary Men by Christopher Browning. It makes you confront your human nature by showing how a normal group of middle class men in a reserve unit in Poland during WW2 and became either murderers or stood by and facilitated what happened. They weren't coerced and normal societal pressure and norms allowed the worst part of our humanity to rear its head.

It is pretty chilling, but makes you confront head on just what you are likely capable of in those kind of situations. I think it is important to recognize that and fight against allowing those kind of pressures to turn you into something you aren't. Absolutely this is an extreme example, but can be applied to all kinds of lesser behaviors which we are susceptible to.