Some books about focus:
“The 8 Traits Successful People Have in Common: 8 to Be Great” by Richard St. John. Richard’s Focus talk has 998 words. The Focus chapter of his book has 4,334 words, about four times more content and depth.
“Focus: Elevating the Essentials to Radically Improve Student Learning” by Mike Schmoker
“Your Brain at Work: Strategies for Overcoming Distraction, Regaining Focus, and Working Smarter All Day Long” by David Rock
“Focus: A simplicity manifesto in the Age of Distraction” by Leo Babauta
“The Power of Focus” by Jack Canfield, Mark Victor Hansen and Les Hewitt