China Clipper: Age of the Great Flying Boats by Robert Gandt (republished 2013)(**)
A thoroughly researched history of the magnificent flying boats that once cruised the world’s skies in the days before World War II. A must for every serious Pan Am bibliophile.
https://www.amazon.com/China-Clipper-Great-Flying-Boats-ebook/dp/B00ER800LU/