What to read after The Critique of Pure Reason?

Kant published the Critique of Pure Reason in 1781. It is very long and almost unreadable due to its dry prose and complex terminology. Kant tried to ease his readers' confusion by publishing the Prolegomena to Any Future Metaphysics two years later. While it is hardly a page-turner, the Prolegomena is much briefer than the Critique and much more accessible in style, making it a valuable entry point to Kant's metaphysics and epistemology. Kant's primary aim is to determine the limits and scope of pure reason. That is, he wants to know what reason alone can determine without the help of the senses or any other faculties. Metaphysicians make grand claims about the nature of reality based on pure reason alone, but these claims often conflict with one another. Furthermore, Kant is prompted by Hume's skepticism to doubt the very possibility of metaphysics...