About The Power and the Glory (no spoilers)
The Power and the Glory is a gritty book about a priest who’s on the run during the peak of Anti-clericalism in 1930s Mexico. It's largely a "fugitive on the run" type of book and centers on a flawed priest who struggles with his shortcomings while continuing to fulfill his responsibilities to do God's work. Although this book appears in the "Christian Fiction" genre, the story itself doesn't have an explicitly religious message and can be enjoyed by readers of all beliefs. This should give you enough to go off without giving away any spoilers.
What happens in the book
If you're looking for spoilers then here you go: he sloughs through various regions of (I'm assuming southern?) Mexico for what seems to be a few weeks gets captured, and then shot. Yeah - that's basically what happens in 225 pages. But that's not really what the book is about, it's much more about exploring his personality on the journey to the inevitable end.
The most interesting part of The Power and the Glory is not necessarily the fact that the priest is on the run, but more so the fact that he's a priest that's not perfect. You'll quickly come to find out that the priest (he has no name in the book) has several shortcomings, namely that he's addicted to whiskey and fathered a child out of wedlock during one of his benders. And although he has his shortcomings, there is some sort of internal drive that does keep him committed to his religious duties.
You'll see this commitment throughout the book when he's hopping from one town to another, trying to outpace the police. Whenever he lands in a new village, the townspeople always want him to hold mass and confessions for them. In nearly every case he does it for the people he comes in contact with, albeit reluctantly. And that's where his imperfectness comes out. He's supposed to be a priest but he goes about his religious duties like someone who's hungover and forced to go to work the next day.
He also doesn't seem to be the kind of person that got into the priesthood because of his commitment to God either. You'll see throughout the book that he looks back fondly on his days in the church, not because of the souls he saved, but because of the good times he had living a life of comfort. It's almost as if the priesthood for him was more of an esteemed career than a higher calling.
In terms of overall "mood" during most of The Power and the Glory, you'll feel when reading it like you need to take a shower. If you've ever gone camping near a river that's largely what it seems like this guy is doing. Most of his travels take place in the dead of night, his clothes have been ruined, and he's surrounded by various grimey traveling companions along the way. And for the most part, the book goes on like this the whole time: grimeyness, new village, say mass, cops come, run, repeat.
About halfway through the book the police are always on his trail and start executing villagers in an attempt to get people to talk. This, along with the fact that he's growing weary of his life on the run, and his will to go on begins to break. He's eventually caught and gives in. The police capture him, he's brought in for questioning, and eventually executed by firing squad without trial.