This particular version of the story Joaquin Murieta was written sometime around 1854. This is a reprinting based on what a Joseph Henry Jackson (who writes this 50 page preface to this thing) claims is the only known existing copy of this first version of Yellow Bird (or John Rollin Ridge as he was also known) wrote. So Jackson felt it necessary to add all these details about the history of Murieta, what is known and what was made up, the way the legends shifted in the telling over the subsequent 100 years.
In the early 1850s, there were believed to be roughly 5 different Joaquins, all with different surnames, running around leading bandit gangs through the mining camps and towns of California. The governor eventually commissioned a Captain Love to gather a posse of sorts and hunt down at least one of the Joaquins. Love succeeded in killing someone he claimed was Murieta, along with a 3-Fingered Jack. They put the alleged Murieta's head in a jar to preserve it and put it in a museum. There's no way of telling whether they got the right guy - odds are they didn't - but the powers that be were satisfied this would convince the public they weren't wholly incompetent, and that seemed to be good enough.
This seemed a sufficiently interesting end that Murieta became a folk hero of sorts, or at least a notable person, and Bird/Ridge was only one of many who tried to cash in. Ridge heaps misfortune upon Joaquin, as within the span of two pages, the bold young immigrant from Mexico is driven from his successful mining claim (and sees his lady love raped, though he is not so much a cad as to desert her) by Americans, is run off his farm by Americans, and is whipped when he rides what turns out to be a stolen horse he was loaned by a half-brother into town, and then sees said half-brother hanged by, you guessed it, Americans!
At that point, Joaquin decides to take vengeance on everyone, stealing horses, robbing miners, old women, random passerbys, and sure, you could sort of excuse it by saying these are all people benefiting from the system that persecuted him and other people who came up from Latin America, but he also robs Chinese immigrants and jeez, didn't they have enough trouble already?
The way Yellow Bird writes it, you can't quite tell whether he admires Murieta or not, or whether we're supposed to or not. He typically describes the men who pursue Joaquin as being good and noble sorts, and laments that they often die in their attempts to capture him. And he'll describe Murieta as having some demons or shadow that protects him, which doesn't make him sound particularly good, but he also spends a lot of time telling us little anecdotes where Joaquin shows mercy, or honors someone who stands up to him, or whatever.
Jackson speculated that Yellow Bird put a lot of himself into Murieta, as Yellow Bird's father and grandfather were killed by a rival faction in the group of Cherokees he grew up with, and Yellow Bird was never able to take revenge. All his attempts to rally people to help fell apart, but Joaquin is able to recruit dozens to his gang, plus many successful ranchers who help or look the other way. Yellow Bird tried his hand at both farming and mining when he moved West, but failed at both. Joaquin is successful, but ruined by the prejudices of others.
So maybe Yellow Bird couldn't stand to make Murieta a true villain, or else he figured that wouldn't be as profitable, not that it worked out for him monetarily anyway. I wouldn't say the story is well-written necessarily, but it keeps moving. Murieta rarely stops and never reflects or muses upon his actions. There's always another near-escape or gun battle to have. Problem being I can't decide whether I want him to escape or not.