Where would one read to get a good history of early Mormonism?

It depends on what your timeframe is for "early." This is typically defined as from the 1820s to 1844 when Joseph Smith was killed, and perhaps a little of the aftermath as the Mormons prepared to migrate west to the Great Basin. Smith officially founded the church in 1830, but events that happened before that helped explain the founding. Because Smith's life was so intertwined with the church, a biography of him and a history of early Mormonism can almost be seen as one and the same.

I'd suggest starting with Richard Bushman's "Rough Stone Rolling." But if you want something more in-depth that covers the earliest period, you might go with Richard Van Wagoner's "Natural Born Seer," which ends with Smith's move from New York to Kirtland, Ohio. There are hundreds of scholarly books and articles that cover various aspects of these years, from Smith's treasure-seeking to biographies of his early associates.

If you want something broader, Matthew Bowman's "The Mormon People" is a very readable, accessible book that covers the entire history of the church. While it has to be brief in its treatment of individual topics, I think Bowman has done a marvelous job of touching on all major events while maintaining an engaging narrative. And if something catches your eye, there will be several more books you can pick up.

I always remind people that all history is contested, and Mormon history is especially contested. It's only been in the last two decades or so that Mormon studies has been able to flourish without a constant polemical push and pull. That's not to say that books weren't written prior to 2000 that weren't any good—there were several. But these writings and Mormon studies generally was almost always approached with skepticism. Mormons asked, "Are they for us or against us?" Attempts at neutrality were equated with anti-Mormonism by many members of the church. In the 1970s, when professional historians began working for the church, church leaders quickly became alarmed and turned against them. Non-LDS scholars questioned if believing academics could approach the history of the church with any measure of objectivity. And most people dismissed the church as silly and unworthy of such study, particularly its scriptures. The South Park episode on the Mormons pretty much sums up how a lot of people felt, and still feel.

I say all of that because even recommending books on Mormonism can be a loaded issue for a lot of people.