Hume's Ethical Writings by Alasdair MacIntyre is an excellent read. I would highly recommend this volume to philosophy students who are studying Hume beyond the "Enquiry". Some knowledge of the religious writings of Hume should also serve as a prerequisite. For this I would recommend, Religious Writings of Hume by Anthony Flew, and Dialogues Concerning natural religion by David Hume, and Richard H. Popkin (editor). This is not a book to read as one would read a novel. It should be digested slowly and methodically.