Meh. These are short stories from the 1840's to the 1860's, telling about colorful characters the author presumably met (or synthesized from people he met) while living in and around Sacramento at that time. It's like a more rustic version of "Little House on the Prairie" (more marital infidelity, venereal disease, illegitimate kids, etc) or a lamer version of the Hollywood Westerns of the 1940's, 50's and 60's (less gunfights, more legal disputes over water and land rights; no pony express, no stagecoaches or trains getting held up, lots of hard work in the mines and trying to make ranches profitable, etc.)
It's probably quite realistic. (What do I know?) I just wish it was a little more entertaining.
Side note: I always thought the big innovation that Mark Twain brought to literature was writing dialogue in a way that brings out the accents and vernacular of the speakers. Isn't that what made Tom Sawyer such a hit? That was published in the 1870's. These stories predate that... some by 30 years, and they're FULL of that kind of dialogue. I wonder why Harte never got any credit for that.