Scruton, Roger Kant. New York: Oxford University Press, 1982.

From the publisher:

Emphasizing the continuity between his moral and aesthetic doctrines and the metaphysical basis in which they rest, the author explores Kant’s relation to Leibniz and Hume, and his attempt to construct a philosophy which was neither rationalist nor empiricist, and could display the limits of human understanding; he shows that Kant was not only a master of philosophical criticism, but the greater defender of the objectivity of human knowledge, in both the scientific and the moral spheres.