Joseph Smith: Rough Stone Rolling by Richard Lyman Bushman
It took me quite a while to get through Bushman's excellent, scholarly biography of Joseph Smith, and I'm proud of myself for it, in a silly, ridiculous way. After all, I'm a fiction-reader at heart, and this is a big book! And scholarly!
It really is excellent, though, and covers everything you've ever heard about Joseph Smith. He puts Joseph into the context of his own time and, maybe most importantly for me, helped me understand what Joseph and Emma's marriage may have been like. I thought it was wonderful.