Gary Chapman books in order
8 books in the catalogue, about 36 hours of reading in all; the shortest takes 3 hours and the longest 6 hours.
8 standalone books in the catalogue.
Standalone books
The Five Love Languages 3.7 h 
The Five Love Languages of Children 4.1 h 
The Five Love Languages of Teenagers 5.0 h 
The Five Love Languages for Singles 4.5 h 
The 4 Seasons of Marriage 4.0 h 
Love Is a Verb 6.5 h 
Things I Wish I'd Known Before We Got Married 3.5 h 
The 5 Languages of Appreciation in the Workplace 4.8 h