Start with high-confidence customer relations books, then narrow by subgenre or adjacent topics.
Customer Success
Nick Mehta, Dan Steinman
Self-improvement 101
John C. Maxwell
Raise the Bar
Jon Taffer
The Experience Economy, With a New Preface by the Authors
B. Joseph Pine II, James H. Gilmore
Customer Satisfaction Is Worthless, Customer Loyalty Is Priceless
Jeffrey Gitomer
Superfans
Pat Flynn