Start with high-confidence grandparenting books, then narrow by subgenre or adjacent topics.
Grandma, I Need Your Prayers
Quin M. Sherrer, Ruthanne Garlock
The Power of a Praying Grandparent
Stormie Omartian
Grandparenting
Phyllis J. Le Peau, Andrew T. Le Peau
Grandmother, I Want to Hear Your Story
Jeffrey Mason