Project Gutenberg Distributed Proofreaders (PGDP) recently released a free ebook of The Pioneer Trail by Alfred Lambourne, who crossed the plains in the 1860. He’s also notable for being the first artist to paint Zion Canyon and for that sweet painting of the Hill Cumorah in the Salt Lake Temple. In this book (which, full disclosure, I haven’t yet read) he describes the experience of crossing the plains.
I can tell you, though, that PGDP is awesome. They’re responsible for a bunch of the Mormon books on Project Gutenberg, including Jesus the Christ, along with most of the other books, period. The quality of their work is generally excellent, and this is no exception. Give it a look.