The Screwtape Letters by CS Lewis

Imagine getting your hands on the other team’s playbook. That is what The Screwtape Letters by C.S. Lewis is like. This book is a satirical collection of letters from a senior demon to a junior demon about how best to pull humans away from God. Every page is filled with devilish advice and brings to light all the tactics used against us. Once you know the other side’s plays, and spoiler: they are not that complicated, it becomes easier to defend against them.