The brilliant one-time lawyer and Warren Buffet partner Charlie Munger (I think the cynical - or should I say skeptical - Munger does the deep thinking, and Buffet is the practical guy) loves Robert Cialdini, who writes about influence and persuasion. Here's Cialdini's The Psychology of Persuasion.
(Also, a lifetime of thought is condensed in Poor Charlie's Almanac: The Wit and Wisdom of Charles T. Munger)