Can a professor at HBS be underappreciated? I believe so. Eric van den Steen is in my view one of the best young microeconomists. He is not a mere technician but rather a dealer in ideas. Oddly, I don't hear his name mentioned often by ordinary, non-frontier economists.
Here is his page of research papers. I am most struck by his paper on the theory of the firm. It is an explicitly Knightian and non-Coasian model of the firm. Unlike many authors, van den Steen does not require that the "firm mode of organization" lower transactions costs in the traditional sense (ever try to get a favor from your purchasing department?).
Instead his model starts with the Aumann model of disagreement and he suggests that control rights in the firm follow from a (figurative) auction over who gets to rule the cooperative venture. It's bidding on the basis of relative certainty to break the initial disagreement. If you bid for the capital goods, and turn the relationship into a "firm," you have greater authority over the other agent, because you can threaten to separate that agent from the capital goods. The winner then installs low-powered incentives because the loser still disagrees with him, and the winner doesn't want the loser to be too motivated to pursue his own vision, thus subverting the winner's orders and recommendations. Overall, the firm increases cooperation among agents but lowers motivation for non-ruling agents and that trade-off determines whether or not a firm will displace a market transactions based on decentralized control of separate decisions.
It's one of the few articles on theory of the firm which make sense to me, the other candidate being Julio Rotemberg's brilliant but poorly explained "A Theory of Inefficient Intrafirm Transactions." I view the Coasian tradition as somewhat of a dead end in industrial organization. Internally, firms aren't usually more efficient than markets although there are good non-transactions cost reasons — including rent-seeking — why they exist.
Here is Eric's paper on the costs and benefits of homogeneity. It's worth reading just about all of his work. Hail Eric van den Steen!