This goes from "you are doomed, everyone", to "you are doomed, everyone, except if god randomly decides to give you grace", to "you are doomed, everyone, except if you are nice, then god has to give you grace" (Pelagianism), to saying that Kant invented autonomy. Along the way, a heap of debris is assembled in some unsystematic, unstructured, wrong, and incomplete fashion that is impressively tedious. Quite the feat, given the subject matter of free will, the good life, rights and obligations and the like. It doesn't help that his style is ashen and that his pontificating over others' views is awkward in poorly demarking what is theirs, what is his interpretation of them, and what are his additions to them.
Those who care would have to adventure through this mess to unearth and assemble the pieces that deal with "imperfect" versus "perfect" rights and obligations, the divergent definition given to them, and the different things assigned to them over time (including eg the relation to moral "perfectionism"). Same for "the Grotian problematic", sentimentalism versus intuitionism and whatever. "Screw that" seems the wiser decision.
This here is supposed to be the triumphant revelation of the book:
"Kant holds that everyone [not just some philosopher king or the Pope] can use the categorical imperative to reason out what they ought to do in particular cases, and to see also why they ought to do it. Bentham made the same claim for his greatest happiness principle, though he did not emphasize its availability to the common understanding as Kant did. They are, to the best of my knowledge, the first philosophers to make such claims."
In tragically comedic fashion, this materializes out of nowhere, after 500 pages and after failing to actually discuss that philosophy of Kant's in any meaningful sense. What it amounts to is the assertion that not contradicting oneself is reasonably possible for everyone, bam, autonomy invented. Skeptics defeated (who had already invented it). Entertainingly, as presented, this would take Hobbes's or maybe Rousseau's contract theory and assert that their political constructs are free of internal contradiction and everyone can and will have the same insight and thus the same "general will/volonte generale". (Or just go back to Plato and the contract theory there, to justice as knowledge, and assert everyone is a philosopher king.) The supposed "invention" by Kant would amount to nothing more than the psychological claim that "people are intelligent/reasonable enough". (Puzzling how things go so wrong in reality. I guess it's not that people are too stupid, they are just too weak. Back to religion.) There follows some meandering skippy rambling on how Kant tied this to the philosophy of Jesus Christ. Which casts yet more doubt. Magisterial.