Lone Star Rising: The Texas Rangers Trilogy (2003), by Elmer Kelton

In general, "western" novels tend to be light on actual history, so I haven't read many. I made an exception for Lone Star Rising: The Texas Rangers Trilogy (2003), by Elmer Kelton, after reading a very interesting straight history work called Empire of the Summer Moon : Quanah Parker and the Rise and Fall of the Comanches, by S. C. Gwynne (2011).

As expected, Kelton's novels contain few historical events or characters, although he does attempt to be even-handed in characterizations of the different peoples involved: Texans, Comanches, Spanish-speaking New Mexicans. Critical historical factors are underplayed or ignored entirely - particularly the role of European diseases in the catastrophic destruction of all Native American tribes. In my 5 criteria, I'd give the novels 2s or maybe 3s across the board. It was a fun read, however, and Kelton is a skillful teller of tales.

For a good account of west Texas history in the middle 1800s, get Gwynne's book instead. Readers might question the characterization of the Comanche as "the most powerful Indian tribe in American history", but Gwynne makes a strong case.

P.S. A few more thoughts about why this novel didn't mention smallpox or cholera. "Western" novels have some archetypical characteristics. One of those is anthropocentrism: the view that "man is the measure of all things". That viewpoint can't stand up to the fact that disease had far more to do with the near-extinction of native Americans than any deliberate actions by humans.

 A dualistic good-evil morality is another staple of western novels. The "good" people struggle to meet and overcome challenges, while the "evil" people act badly. Smallpox and cholera, however, don't care who's good and bad. The universe doesn't care about humans. That point of view doesn't work in a western novel.

The Sot Weed Factor, by John Barth

No one failing to read The Sot Weed Factor until 2015 can claim to be among the cognoscenti of historical fiction. So be it. It's still a great post-modern American novel - not just a great hist-fict novel, and still merits commentary 55 years after its publication. Lacking the qualifications for a more general review, the focus here will be on the historical aspects of the novel. For more, a Google search will lead to numerous reviews, discussions, plot summaries, etc.

Barth's historical jumping-off point was a satirical poem published in London in January of 1708, attributed to one "Eben. Cook, Gent.". The complete title is The Sot Weed Factor: Or, a Voyage to Maryland. A Satyr. In which is described, The Laws, Government, Courts and Constitutions of the Country; and also the Buildings, Feasts, Frolicks, Entertainments and Drunken Humours of the Inhabitants of that Part of America. In Burlesque Verse. 

I found a copy (literally - photocopied pages of the original) of this composition at my local Santa Cruz Public Library, and read it along with Barth's extrapolation. I recommend the exercise, despite the archaic language and spellings (e.g. "alfo" rather than "also") It's truly impossible to imagine any other author composing such a fantastical fictional framework for Cook's "satyr", and yet one which is plausible (barely) and remains true to the paucity of known historical facts. Highly entertaining, hilarious, iconoclastic, raunchy, cynical - in other words, a John Barth novel.

The five criteria:

1. Did the novel inspire me to further historical research?

Yes. Readers of Barth will know that he hails from the Chesapeake Bay's Eastern Shore region, so it's no surprise that he took an interest in Cook's narrative, which was set largely in that remote and lightly-populated part of Maryland. The colony of Maryland experienced great turmoil in the later 1600s, mirroring the final stages of Catholic-Protestant strife in the home country. Barth introduces the reader to many of the historical events and personalities of those times, although none of them are central to the story. For that reason, in order to more fully understand the historical context, I was inspired to learn more from other sources.
Score = 5

2. Did the novel include enough history to make it an interesting historical story?

Yes. As noted above, the major political events of late 1600s Maryland are a backdrop rather than central to the novel's story. A point is subtracted for that reason, but the fictional action has numerous intimate connections to its historical context. Barth's complex plot even manages to encompass the John Smith-Pocahontas story - irreverently, of course.
Score = 4

3. Was the depiction of historical events accurate?

Hard to say. The only accounts of most of these events were written by participants, and usually by only one participant. Knowing the tendency for first-person accounts to be highly colored - if not outright falsehood, it's just barely plausible that these events happened exactly as described in The Sot Weed Factor. Let's just say that no blatant and obvious contradictions were found.

At the end, Barth included a sort of Historical Notes epilogue, titled The Author Apologizes to His Readers. Some of the historical (and novelistic) loose ends get wrapped up, and I always appreciate that sort of effort by historical novelists.
Score = 3

4. Was the depiction of historical characters accurate?

Again, hard to say. Similar to criterion 3, the novel's primary goal was not to investigate and accurately describe historical events and characters. There's no contradiction with the little we know for sure, but that left Barth vast spaces to fill with fiction.

Most of the major historical characters remain offscreen throughout the story, spoken of in the third person. One who has a brief spoken part is Francis Nicholson - at that time Governor of Maryland.

For the 1987 Anchor Books (Random House) edition, Barth composed a Foreword containing much more historical background on Ebenezer Cooke (spelled with an "e" at the end, despite the original printing) and the historical research underlying the fiction. That inclusion raises the score from 3 to 4.
Score = 4

5. Were the fictional or fictionalized plot and characters plausible?

Yes - from a modern perspective. Really, though? - probably not. But the same can be said of any historical novel, so that's not a criticism. Maybe the best approach is to say is that the novel challenged a lot of conventional narratives, causing the reader to devote serious thought to those long-ago happenings rather than simply accepting the standard stories as backdrops to the fictional action.
Score = 4