"Grace, Actual and Habitual: A Dogmatic Treatise" by Joseph Pohle
Pohle was an ordained priest who taught in Switzerland, England, and more. As a man of faith, he was uniquely qualified to speak on the topic of grace from a biblical and philosophical understanding. Covering everything from the nature of grace to the existence of free-will, this book wasn't just written for Christian or Catholic audiences, but for anyone interested in philosophy and understanding life.