In the wake of WWI, a quack Kansas surgeon became a hero of the people — and an enemy of the American Medical Association — when he touted the discovery of a particularly beastly cure-all: testicles transplanted from goats. With a mix of down-home charm and breathless storytelling, Pope Brock’s chronicle of ”Dr.” John R. Brinkley, Charlatan, makes for a compelling slice of lurid Americana. But the author’s gee-whiz tone, while fun to read, doesn’t leave room for a deeper portrait of a mad genius who may ultimately have had more in common with Jack the Ripper than P.T. Barnum. B?