The Invisible Hook takes a rational choice framework and applies it to the golden age of Anglo-American piracy. The resulting ideas are compelling and fun, and Leeson presents them enthusiastically and clearly. He's excited about pirates, at least as much as he is about econ, and he wants to set the record straight. "Pirate fiction portrays seamen as choosing piracy out of romantic, if misled, ideals about freedom, equality, and fraternity," but Leeson knows the reality was less about utopia and more about "piratical means, used to secure cooperation within pirates' criminal organization, rather than piratical ends, as they're often depicted." And just about all pirate actions will come down to this.
Leeson makes no claim to being a historian and makes free use of secondary sources to present the historical record, aiming to interpret that record through the lens of economics. But still, there was plenty for me to learn about the basic history as well: the difference between buccaneers and pirates, for example, or the importance of the quarter-master on a pirate ship. Also the great size of pirate crews in comparison to those of merchantmen, and the truly great potential prize available to pirates in their golden age. And just about everything there is to learn about pirates is interesting. The romantic nature of the subject is really inescapable.
That remains true even when the motives of the outlaws are unwoven. Leeson contends that "only with economics can we make sense of a great deal of otherwise unintelligible individual behavior." It's the only way to understand a group made up seemingly of "libertarians who conscripted nearly all their members, democrats with dictatorial captains, and lawless anarchists who lived by a strict code of rules."
All these seeming contradictions came about because pirates were in unusual circumstances that produced correspondingly unusual incentives. One of the biggest differences between pirate crews and those of legitimate ships, be they merchant or military or even privateer, was the democratic governance of the pirate ship as opposed to the autocratic powers of all other captains. Were pirates just unusually progressive? Probably not; but they lacked an absentee owner and corresponding principal-agent problem. Since pirate ships were stolen, the pirate crews owned them collectively, and they had no need of an autocratic captain to align the interests of the ship's owners with those of its crew--they were already one and the same. In that sense, their very criminality was "the source of pirates' ability to use this system" of "democratic checks and balances."
There are like explanations behind pirates' other surprising habits, all satisfying but not necessarily surprising--especially if you're already given to thinking about such matters from this point of view. But bringing them all together with compelling information about historical events makes for an engaging book.