Warrior Poet said:
Blood Meridian, or the Evening Redness in the West by Cormac McCarthy. Not only is it one of the best westerns I've ever read, it's one of the best works of literature I've ever read. I'm a huge McCarthy fan, but this is his best as far as I'm concerned.
Glad to see some more McCarthy love!

I had a writing tutor in college who introduced us to McCarthy, both as a guy who could set a scene and a guy who could build character through dress. Both excerpts were from
Blood Meridian: the former involved resonant earth, and the latter involved a wedding dress. If you've read the book, I'm pretty sure you know what I'm talking about.
The bit about its being fine literature is also no joke. It's probably not the best literary work I've ever read, but it's undoubtedly
literary in even the snootiest sense of the word: despite being a gripping tale with plenty of plot, it's also very well respected in literary circles, with McCarthy being so good that there's actually a backlash against him. The backlash article I read awhile ago was pretty silly IMO, but it was interesting nonetheless.
And yeah, it's my favorite of teh three or four books I've read by him. His other books are good, but they weren't forces of nature like this one was.
Finally, one more suggestion: if you're looking for a lyric, epic, true-to-history account of the Old West, you can't go wrong by avoiding
Rustler's Rhapsody, which is none of those things, but is pretty hilarious in a goofy slapstick way.
Daniel