In case anyone is interested, I picked up a book that may be something of a complement to Harris. It is a more academic treatment of moral philosophy, but I think it is fairly accessible. It comes highly recommended by someone I know, I haven't started reading it yet
Michael Huemer, Ethical Intuitionismhttp://www.amazon.com/Ethical-Intuition ... 290&sr=1-1
'Read this. It is the best book ever written on meta-ethics. Even philosophers who know the field may feel as though they are confronting these issues for the first time. I used to think of ethical intuitionism as a silly, naIve, even ridiculous theory, but Michael Huemer has made an intuitionist out of me.' - Stuart Rachels, Department of Philosophy, University of Alabama, Tuscaloosa, USA 'Huemer's book may be the best, most comprehensive defense of ethical intuitionism since Moore's Principia Ethica...[it] is an outstanding defense of the view that there are objective moral truths knowable through intuition. Whether or not one agrees with Huemer's conclusions, one cannot ignore the power of his arguments.' - Richard Fumerton, Department of Philosophy, University of Iowa 'A terrific book. Now philosophers will have no excuse for treating ethical intuitionism as if it were a silly and easily-refuted view.' - James W. Nickel, Arizona State University College of Law, USA
A defense of ethical intuitionism where (i) there are objective moral truths; (ii) we know these through an immediate, intellectual awareness, or "intuition"; and (iii) knowing them gives us reasons to act independent of our desires. The author rebuts the major objections to this theory and shows the difficulties in alternative theories of ethics.
More from the author's web site: http://home.sprynet.com/~owl1/book2.htm
There were several very cheap used copies on Amazon, but they're not there anymore (I bought it for $2 plus shipping).