The American Catholic Quarterly Review recently published The Order of Love in Thomas Aquinas by David M. Gallagher. The article discusses the concept of ordo amoris. Here is Gallagher's conclusion:
The order of love, then, is not a simple ranking of persons from nearest to farthest. To ask whom I should love more is to ask at least three further questions: whether “more” means a greater good or a more intense love; whether the person in question is better, or nearer to me, or both; and within what kind of friendship the question arises. Thomas’s answers yield a pattern at once realistic and demanding. I should rejoice in the greater goods of those who are better, even if they are strangers to me; I should labor most for those who are nearest, beginning with myself; and I should love God more than all, myself included, because in him I find my own good, and every good I share with others, in its perfect form.