I went to North Texas State, where McMurtry was the big deal alum among the English teachers. He's written a lot of great stuff: "Lonesome Dove," "Last Picture Show," "Terms of Endearment," and more. Of course, he's also written a lot of hard-to-get-through wanking. As a general rule, his western stuff is better than his contemporary stuff (aside from "Terms"), and his sequels aren't as good as his originals. If you loved "Lonesome Dove," avoid "Streets of Laredo" and preserve the memory.
Lonesome Dove was one of the few books/movies that, when it ended, it left me frustrated. I wanted to turn the page and see what happens next. To me, it was the perfect western.