Books about Ethics
Henry Hazlitt's The Foundations of Morality took the classical view of ethics, debunking usual mistakes and fallacies, reaffirming the essence of what must be retained. It was a necessary cleanup and restatement of ethics; however, it didn't try to study the nature of the foundations of ethics but to explore what kind of ethics can stand firmly or not on its foundations.
Thus, Daniel C. Dennett's Freedom Evolves can be seen as a complementary text. It establishes the modern foundations upon which ethics can be rebuilt, and related to the sciences of nature: physics, biological evolution, economics. And at the same time, it avoids to delve in the realm of ethics itself (and reveals several time the wrongheaded statist ontology of the author, though in a few isolated marginal remarks orthogonal to the discourse of the book).
Finally, Ayn Rand, in such books as The Virtue of Selfishness or Philosophy, Who Needs It?, gives rational foundations to Ethics, relating it to Metaphysics and Epistemology. And she even studies the psycho-epistemology of anti-morality.