Here are the resources Dr. Howard "Prof" Hendricks recommends:

Anything by Ken Dychtwald, including Age Wave: The Challenges and Opportunities
of an Aging America

Henri Nouwen, Aging: the Fulfillment of Life

Howard Eyrich and Judy Dabler, The Art of Aging

Ken Johnson, Pursuing Life with a Shepherd’s Heart

Nancy Mace and Peter Rabins, The 36-Hour Day