When my company was faced with a sudden 40% drop in revenue I saw a way to make a turnaround in "from worst to first" by Gordon Bethune, a book about a $400m turnaround done in 12 months : http://www.amazon.com/From-Worst-First-Continentals-Remarkab...

After getting out on top after my turnaround, Simon Sinek's "Start with why" helped me figure out why I am running my business the way I am, and how I can use that to do even better : http://www.amazon.com/Start-Why-Leaders-Inspire-Everyone/dp/...