It is extremely difficult to give this book a rating. In the first part, it is a great book. It's Calvin. Calvin is an incisive writer, a first-rate thinker, and committed to the glory of God. The substance is quite good, even if it's not a subject Calvin dedicated much time to writing on over the course of his life.
Yet the volume itself leaves much to be desired. In the first part, large sections (particularly in the selections from "On Christian Liberty" in the Institutes & parts of the selections from the commentary on Daniel) do not deal much with political duty in the first place. While interesting and useful in themselves, someone eager to read on the relationship between God & political duty is bound to be a bit frustrated. Additionally we are given nothing but the text, so do not expect helpful explanations of the relationship between Calvin's thinking & his predecessors or contemporaries. Not a terrible thing, but it would have been a nice value-add for a volume with so little subject matter relating directly to the notional subject.
All the same, any Calvin is good Calvin. This reading is particularly a healthy antidote to two groups common in so-called "Calvinist" circles today. First, Calvin does directly address the relationship between divine law & civil law in a helpful way. In doing so he clarifies helpfully the way divine law as instantiated in the Mosaic code relates to present-day magistrates & we find a useful proleptic refutation of modern Theonomists of the stricter kind. Second, Calvin's view decisively excludes any kind of libertarianism. He even spends a significant amount of time refuting the idea that wicked rulers cease to wield legitimate authority, a common fig leaf for the more anarchic among Calvinist circles.
All in all—it's fine. Calvin is great. The compilation is so-so.