The Invention of Autonomy

At the beginning of The Invention of Autonomy, J.B. Schneewind modestly explains that he began work on the book "because there were many aspects of Kant's moral philosophy I could not understand," and he therefore sought to understand Kant's remarkable contribution to moral theory by considering it in its historical context. By the time one finishes reading the book, over 500 pages later, it's reasonable to question if there's anything about modern moral philosophy that Schneewind fails to understand.
The Invention of Autonomy is divided into four main parts. In the first part, Schneewind discusses the natural-law theory of morality, as classically expounded by St. Thomas Aquinas, and traces its rise and fall by considering the works of Luther, Calvin, Machiavelli, Montaigne, Charron, Suarez, Grotius, Hobbes, Cumberland, Pufendorf, Locke, and Thomasius. The second part deals with perfectionist approaches, as exemplified by Herbert of Cherbury, Descartes, the Cambridge Platonists, Spinoza, Malebranche, and Leibniz. The third part looks at moral philosophers who, by and large, are inclined to regard morality as independent of God's ongoing cooperation. Most of the canonical British moralists, from Shaftesbury, Clarke, and Mandeville to Hume, Reid, and Bentham, are included. Finally, in the fourth part, Schneewind examines anticipations of Kant's invention (or, perhaps, discovery) of autonomy in the works of Wolff, Crusius, the French philosophes, and Rousseau. He then skillfully relates Kant's moral thought to the rich tradition preceding it.