You get a clearer idea of the book with the full title: Margin: Restoring Emotional, Physical, Financial, and Time Reserves to Overloaded Lives by Richard A. Swenson, M.D.
"Overload is the disease of our time. Margin is the cure."
"Margin is the space that once existed between ourselves and our limits. It is something held in reserve for contingencies or unanticipated situations."
It's not that Dr. Swenson is saying something we haven't heard before or shouldn't instinctively know, but it seems we need to keep hearing it. Maybe one day it will sink in and we will say "No" to taking on one more thing.
Life is to enjoy, not endure (not sure who said that). And to paraphrase Stephen Covey, the enemy of the best is the good. We're all doing good things, but when there isn't time to do everything, can we stop long enough to figure out what the best things are?
So another book with practical ideas on creating space/margin in our lives is a good thing.