The Art of War - Sun Tzu

This book really is what the title states - it's the author's method of waging war. I remember when it was a fad to read this book in the 1980s, when "big business" was really getting out of hand and corporate takeovers, etc., were a norm - I think all those MBAs and finance majors got a kick out of thinking that they were some kind of "warriors" with briefcases and contracts instead of actual weapons (although I suppose people do, or can, use things like contracts as weapons quite a bit....). In any case, although of course it's mainly geared toward actual warfare, there are some things I suppose one could apply to daily life, such as this:

During the early morning spirits are keen, during the day they flag, and in the evening thoughts turn toward home. 
And therefore those skilled in war avoid the enemy when his spirit is keen and attack him when it is sluggish and his soldiers homesick. 

Here's another 2 that are very relevant:

One anxious to defend his reputation pays no regard to anything else. 

and

If he is of a compassionate nature you can harass him. 

I feel like I see these things in action all around me these days.

To be honest, based on the topic, this book wasn't something that I was super interested in, but all in all, with the introduction, notes, and other info that was included, I ultimately found it interesting from a historical perspective.