Brother Odd is likely the most Catholic of the Odd Thomas Series. Set in a monastery, there is Catholicism all around. But, trouble seems to follow the Odd one even amidst the chastity, poverty, and obedience of the monks. But, the story is perhaps also the least edgy, for similar reasons.
The villain is a bit of a mystery in this one, and not revealed until late in the book. So, discussing him/her is a bit of a spoiler. Don't read on if that annoys you. I'll try not to spoil too much, though.
The villain is a type of mad scientist. The themes are similar to the Frankenstein story and very Catholic. There are certain discoveries of science that are best left undiscovered or, at least, unexploited. I read one critical review from a reader wondering why the characters would react so negatively to this particular discovery of science (I'm not going to spoil it for you) because it would be, like, totally cool. But if you are Catholic, it makes total sense.
A nice aspect of this one is in terms of character arc. A mild criticism I have of Dean Koontz's work is that most often villains are awful and stay awful (really awful) and good-guys are good and stay good unless they are victims of mind control or some other voodoo. I'll not spoil anything, and just say, watch for changes in the characters in this one.
We highly recommend the entire Odd Thomas series, and Brother Odd, in particular, gets extra marks for its more overt Catholicism.