Indeed, it is a collection of portraits. I stopped on those of Montesquieu, Comte, Tocqueville, and especially Marx.
R. Aron's biases did not bother me; quite the contrary: Aron is a talented philosopher, sociologist, and good guide. As a "Marxian," as he defined himself, I particularly appreciated his introduction to Marx's thought. In it, he shows the relevance of the analysis of Capitalism (of his time, but probably not only) while completely refuting the Marxist political orientations, whose mistakes History has shown.