The Legal Theory Bookworm recommends The Development of Ethics: From Socrates to the Reformation Volume 1 by Terence Irwin. Here is a description:
Terence Irwin presents a historical and critical study of the development of moral philosophy over two thousand years, from ancient Greece to the Reformation. Starting with the seminal ideas of Socrates, Plato, and Aristotle, he guides the reader through the centuries that follow, introducing each of the thinkers he discusses with generous quotations from their works. He offers not only careful interpretation but critical evaluation of what they have to offer philosophically. This is the first of three volumes which will examine the history of ethics in the Socratic tradition, up to the late 20th century.
And here is the table of contents:
I. Introduction II. Socrates III. Cyrenaics IV. Cynics V. Plato VI. Aristotle: Happiness VII. Aristotle: Nature VIII. Aristotle: Virtue IX. Aristotle: Virtue and Morality X. Scepticism XI. Epicurus XII. Stoicism: Action, Passion, and Reason XIII. Stoicism: Virtue and Happiness XIV. Christian Theology and Moral Philosophy XV. Augustine XVI. Aquinas: Will XVII. Aquinas: Action XVIII. Aquinas: Freedom XIX. Aquinas: The Ultimate End XX. Aquinas: Moral Virtue XXI. Aquinas: Natural Law XXII. Aquinas: Practical Reason and Prudence XXIII. Aquinas: The Canon of Virtues XXIV. Aquinas: Sin and Grace XXV. Scotus: Will, Freedom, and Reason XXVI. Scotus: Virtue and Practical Reason XXVII. Ockham XXVIII. Machiavelli XXIX. The Reformation and Scholastic Moral Philosophy
I look forward to the next volume. The complete work promises to be an essential reference work, and essential reading on the history of ethics. Very highly recommended–it belongs in the library of anyone with a deep interest in moral philosophy generally or normative legal theory in particular.