To get away from just Presidential political history I read the first half of Leonard Arrington's "Brigham Young: American Moses." Of course Young's story cross several decades, but I stopped reading in the 1850s. Not because of trying to limit the time period, but because the book was a little too dense. I had the most basic understanding of Mormonism going into the book, but I feel that it was written for people who have a much stronger foundation in understanding the faith. If I remember correctly the author was (is?) an official historian for the chuch in Salt Lake City and has access to a lot of detailed records. And that's how the book reads--written by someone with tremendous resources, but who is also very close to the subject matter.
As for the life of Brigham Young--Fascinating.
(Read April 2008)