On Aristotle's Politics (350 BCE), books 1 (ch 1-2), 3, 4 (ch 1-3), 5 (ch 1-2), 6 (ch 1-6), and 7 (ch. 1-3, 13-15).
Aristotle provides both a taxonomy of the types of government, based on observations of numerous constitutions of the states of his time, and prescriptions on how to best order a state. These are meant to be practical; though he does spend some time on the "ideal" government, he recognizes that that's going to be very rare, given that it requires those in charge to be virtuous according to his stringent standards. He provides advice for all the types, whether rule by one, or the few, or the many, to help keep them stable and from drifting into their corrupt forms. He sees the state as a natural outgrowth of human nature, and that one can characterize the health of a state in much the way one can describe the health (i.e. virtue, happiness) of an individual. Yes, he's a major league elitist, but there's still some good stuff here, applicable even to modern times. Read more about the topic and get the book.
End song: "Don't Forget Where You Are," from the Mark Linsenmayer album Spanish Armada, Songs of Love and Related Neuroses (1993), newly remixed/remastered.