I wish I had read this as an undergraduate, especially the opening chapter in which Kagan discusses and contrasts various theories of well-being: mental state theories, desire-based or preference theories and lastly objectivist theories.
All in all, this is a really solid overview and detailed explanation of the various foundational moral theories and concepts. I particularly liked Kagan's definition of deontological theories in terms of constraints which have independent normative force and are not just rules of thumb. This I think is much clearer than framing deontology as, inter alia, the simple rejection consequentialism or a theory which either affirms absolute rules or assesses an act in terms of its intrinsic character. Kagan is right that these latter framings are inadequate even though they are bandied around.
Although consequentialism and deontology are often presented as diametrical opposities, Kagan argues convincingly that there is considerable overlap between them, as deontological theories can also value good results. Here Kagan distinguishes between moderate deontological theories and absolute deontological theories, the difference being that on the former, but not the latter, constraints come with certain thresholds (in terms of good results) which may lead them to being outweighed or overridden.