Reinhold's Letters on the Kantian Philosophy is arguably the most influential book ever written concerning Kant.

Introduction; 1. The need for a Critique of Reason; 2. The result of the Kantian philosophy on the question of God's existence; 3. The result of the Critique of Reason concerning the necessary connection between morality and religion; 4. On the elements and the previous course of conviction in the basic truths of religion; 5. The result of the Critique of Reason concerning the future life; 6. Continuation of the preceding letter: the united interests of religion and morality in the clearing away of the metaphysical ground for cognition of a future life; 7. A sketch of a history of reason's psychological concept of a simple thinking substance; 8. Continuation of the preceding letter: the master key to the rational psychology of the Greeks; Appendix: the major additions in the 1790 edition.