What to read after Critique of Practical Reason (Kritik der praktischen Vernunft)?

"The Critique of Practical Reason" is the second of Immanuel Kant's three critiques, published in 1788. It follows on from Kant's first critique, "the Critique of Pure Reason" and deals with his moral philosophy. While Kant had already published one significant work in moral philosophy, "The Groundwork of the Metaphysic of Morals" (1785), the "Critique of Practical Reason" was intended to both cover a wider scope and place his ethical views within the larger framework of his system of critical philosophy. The second Critique exercised a decisive influence over the subsequent development of the field of ethics and moral philosophy, beginning with Johann Gottlieb Fichte's Doctrine of Science and becoming, during the 20th century, the principal reference point for deontological moral philosophy.