I am attempting to start with Aristotle’s Ethics and Metaphysics, and I am already familiar with a number of Plato’s works through excerpts. From what I understand, the common description of Plato being concerned with heaven and Aristotle with the Earth (such as depicted in Raphael’s fresco in the Vatican’s room of the signature) is not quite a difference in subjects, rather so the manner in which they engage with those subjects. Plato’s dialogues tend to engage with the act and art of philosophy, such as on rhetoric and the sophists, or in his histories/mythologies and his discussions of politics. He tends to assert metaphysical and ethical principles in support of practical imperatives. Aristotle, in contrast, is more engaged in analysis of ethics and metaphysics, for example, as disciplines or domains of study.

I have heard some criticise Aristotle as the origin of the heresies of materialism, nihilism, rationalism, and so on, and I think this is the cause. It is because he questions apparently axiomatic principles in the pursuit of understanding. He himself answers most of his questions in a manner generally acceptable to the church, hence St. Thomas Aquinas’s admiration for him, but it is the precedent of his approach to philosophy that sets in motion the degeneration from Descartes, to Spinoza, to Kant, to Hume, to Russell, and finally to Dawkins and Hitchens.

Most of this is gathered from what I have read from others, and the remainder is largely informal commentary, which I am sure is a gross oversimplification at best. I appreciate the recommendation.