A meandering look at the Mormon religion - its history, right from its founder Joseph Smith and his secret proclivities for polygamy, the founding of Utah, through to present-day Mormonism and its many offshoots (notably the fundamentalist Mormons who still practice polygamy). Krakaeur also makes a connection between some of the violence committed by Mormons in its early history with the murders carried out by two fundamentalist Mormons in the present day.
Published in 2003, I can imagine this book did some good towards exposing some of the church's dark sides (for instance it wasn't until 2013 when they stopped discouraging interracial marriage at their youth groups). However it did feel anti-religion and anti-Mormon (although weirdly Krakauer preferred to express this via quoting from books/other resources rather than outright saying it himself) which as a non-religious person I'm fine with but is probably very off-putting for any potential Mormon readers.
I was also expecting more of a "true crime" style novel but instead I felt like there was a lot of jumping around. The author would mention present-day Mormons towards the start of the novel and then reference them again towards the end (although making sure though to remind you who they were) which didn't really help me to connect with their stories.