A modern American academic delving into the secrets of the past sounds like a formula for more Dan Brownish tripe, but “The Arms Maker of Berlin” is an intelligent thriller that is more akin to Le Carre than to Brown. Fepserman’s hero, a college history professor, follows a cryptic trail laid by his mentor, sometimes rival, and former OSS agent. His opponent is a German industrialist who has a shameful secret from World War II. The book has an interesting plot that avoids most of the cliches of the genre, interesting characters, and a more adult style than many recent thrillers.