I would like to take a moment to advise everyone to read The Screwtape Letters. Written by C.S. Lewis, author of The Chronicles of Narnia, this is without a doubt one of the most useful and insightful books on religion and living a spiritual life, ever. Although written by a Christian theologian for a Christian audience, this book is relevant for people of any faith. I have read it a dozen times and will probably read it many more. Each time I read it, I find new insight into my own spiritual life.
The book takes the form of a series of letter from a senior devil named Screwtape to his nephew, Wormwood. The letters advise Wormwood on the nature of sin, the ways in which human beings corrupt themselves, and how best to tempt people into evil. The book is clearly the product of a person who has great insight into the human mind and spirit.
It describes the small hypocrisies and lies that people habitually tell themselves in each other in such a direct and obvious way that nobody but the most dishonest will fail to recognize themselves in the description. It talks about how these small dishonesties are the seeds of the greatest evils, and the ways in which a person can slide from one to the other without even noticing. It discusses love, and the various things that masquerade as it, and goes into great detail about why it is precisely when things are the most difficult that devotion and sacrifice are the most valuable.
In short, it covers topics of interest and value to any person on a spiritual journey, or even any person who is just curious about what makes people the way they are. The sequel, Screwtape Proposes a Toast, is also well worth reading, and goes more into society and politics.