I actually read this book as a teenager and found it fascinating, having gone to high school in Utah.

It gives a clear comparison between Mormonism and Catholicism. It is a very philosophical book in Christian Apologetics. It is written by a Catholic priest who grew up with a large Mormon family.
BEWARE: The Book claims to be unbiased in the beginning, however it slowly unravels itself and grows to a more and more biased book. It have a small description on a topic upon Mormon belief and pages worth of description upon the same topic upon the Catholic belief.

Read as a youth. I would like to reread as an adult.