Beston, Paul. The Boxing Kings: When American Heavyweights Ruled the Ring. Lanham (MD): Rowman & Littlefield, 2017. pp. 357.$36.00 Hardback. Reviewed by Cian Manning.        Paul Beston, managing editor of the City Journal and contributor to the boxing website The Sweet Science, in his study The Boxing Kings: When American Heavyweights Ruled the Ring…