Just for the heck of it, I thought I'd sketch how I'd summarize the outlook (not necessarily the argument, yet) of Lear's book. It ends up being a little different from her way of putting it, or what I find in the reviews, but it's how I'd state it. (Of course, I'd welcome clarifications or corrections from Lear or others.)
Aristotle’s ethics should be understood almost as if a treatise on the ‘natural history of human beings’. From a third person point of view, studying human beings as an Aristotelian would study any other sort of thing in nature, we see that the telos of a human beings is to achieve philosophical contemplation. This means, presumably: human beings form self-sufficient communities (city-states), to provide occasion (‘leisure’, ‘free time’), so that some from among them can achieve philosophical contemplation.
On this picture, it might seem that most human beings, most of the time, fail actually to achieve the telos of human existence. This result should be avoided not least on Aristotelian grounds, because it cannot be that nature for the most part fails to achieve its goal.
We therefore say that any telos can be achieved in either of two ways: directly, or by approximation. A telos is achieved by approximation, when something like the following happens. (I’ll state this very roughly for now, without some important qualifications.) There is a general kind of subjects, the members of which have different aptitudes or endowments. Also, there is a general group of goals, which on objective grounds can be ranked as better or worse. The best member of the kind achieves the best goal, and the other members of that kind achieve goals from that group that differ precisely in relation to their difference in aptitude or endowment. It follows that an analogy (or equivalence of proportions) can be constructed, which licenses the claim that everyone in the group is somehow achieving the same goal.
Aristotle’s star example of this is how living things achieve the telos of being alive. God as an individual lives eternally, without the possibility of not living (immortality). A species of animal (Aristotle thinks) achieves immortality corporately, through reproduction: no individual animal is immortal, but the species lives forever, through reproduction. We can construct therefore the analogy: uninterrupted life:God::uninterrupted reproduction: animal species. The analogy allows us to say that both God and animals are achieving the same thing, but the animals do so by ‘approximation’.
Apply this, then, to human beings. The good of truth attained in philosophical contemplation is the best good available to human beings and greater than the good of truth attained in practical deliberation and judgment. Philosophers, when they contemplate, achieve the goal of human beings directly. But when they cannot contemplate (say, because they have to eat or engage in business), or when others who have no aptitude for philosophy live a life of civic virtue, then (we can say) they are achieving that goal of contemplation ‘by approximation’. The reason is that we can construct an analogy such as the following: theoretical truth:philosophical contemplation::practical truth:actions of the virtues of character.