Harris' Legal Philosophies is a marvellous work. I take up the earlier reviewer's claim that this book is a little confusing; far from it: Legal Philosophies is a clear, lucid, pithy and witty introduction to a fascinating, if often difficult subject. Legal philosophy can be confusing; Harris' approach makes it accessible.
Harris' scope and ability to draw on primary and secondary sources is tremendous. He covers the Anglo-American "canon" of authors that is Hart, Dworkin and Finnis, surveys many schools of thought, including, inter alia legal realism, legal science (he is particularly impressive on Kelsen) and critical legal studies, and provides balanced knowledge and insightful commentary on several major jurisprudential issues: duty to obey the law, the rational behind punitive justice and the relationship between law and morality.
There is no better introduction or general guide to legal philosophy. I advise anyone with an interest in law or political ideas to purchase a copy.