King's book is entirely about ethics, and while he refers to earlier writers (such as Rawls in particular) he seems to be putting forward a new schema, taking the search for value in one's life as an axiom and working forward from there through empathy and obligation towards one's fellow human beings to the Help Principle, that we should help other is the value of our help to them is worth more than the cost of that help to us. The second half of the (short) book works through practical examples of this principle in politics, romance and law.
I am not well enough read in philosophy to know how original all of this is, let alone how fairly King represents the views of other philosophers, but it is a very attractive and comprehensible argument, told in a chatty but far from superficial style. It reminds me most of Zen and the Art of Motorcycle Maintenance, though without the motorcycles, and it possibly has the potential to become a similar cult classic with the right sort of marketing. (Certainly has a catchy title.)