Chapter 6: "The Ultimate Distinctions" is especially helpful to me. Maybe because he's a pragmatist, or because he's a naturalist, or because he's reflecting Dewey's attitude toward metaphysics (and Dewey was especially influenced by Aristotle, as I seem to remember Ralph Sleeper emphasizing), I find Randall's explanation of the Metaphysics especially helpful. Two points in particular stand out.
First, what Aristotle meant by substance, ousia, is most decidedly not what the great Moderns meant by it.
It is significant that when Descartes asked, "What is substance?" he was asking for what persists unchanged throughout change, what is in change that does not itself change. And in Locke and Kant, in fact, throughout modern philosophy, "substance" has been taken as the unchanging, the permanent in change, whether Locke's "I know not what," or Kant's "permanent in relation to phenomena." But for Aristotle, who since he gave the technical meaning to the term ousia rendered into Latin as substantia ought to know, ousia or substantia is defined precisely as that which undergoes change in change, what is at the end of any process different from what it was at the outset. (Randall, 112)
Now, this is an interpretation, and one that I am sure plenty of people will and have protested. No doubt the protests will be even stronger given my note about Randall's own pragmatist philosophical commitments. But his work on Aristotle is especially interesting to me because A) I happen to share a lot of those commitments, and b) it sheds a lot of light on pragmatist metaphysics more generally, especially as a reaction against the Moderns.
Second, Randall emphasizes Aristotle's commitment to the inexhaustible "thisness" of things. Now, Randall had the benefit of writing in the wake of phenomenology; Edmund Husserl and Martin Heidegger taught his generation of philosophers how to attend to things as opposed to language about things. Randall's Aristotle also knows the difference:
existing things, ousiai, are clearly more than their definitions alone, they are more than what they can be truly said to be. Such concrete things can never be exhausted by what we can say about them. We can never exhaustively "define" any particular individual ousia, we can never say everything that is true about it. (Randall 121)
That last point is one that Charles S. Peirce emphasizes again and again; it's the need to always recognize the irreducible, unique haecceity of things, which moors philosophy to actuality. Without it, we get speculative systems that are fantastically satisfying, but misleading.