Under the Banner of Heaven by Jon Krakauer (2004, Paperback, Reprint)

This was a well-researched book. It is about Utah brothers who decide to kill their sister-in-law and her baby because they believe they have been directed to by God. Understanding this crime requires quite a bit of explanation about the origins and evolution of the Mormon Church (Latter Day Saints). That basis is needed to really grasp how the splinter groups (such as the FLDS at the Yearning for Zion Ranch and others)have formed and why. Some feel that the author is anti-Mormon or that he hates Mormons. I didn't find that to be the case. The author claims several times to be an admirer of the church and it's people. Having said that, he doesn't whitewash the church's history or that of it's founders. A fascinating book.