1812 is subtle alternate history -- a "for want of a nail" story, or rather an "if the nail hadn't been lost" story. While Eric Flint is best known for 1632, a novel based on time travel, there are no science fiction or fantasy elements in this novel. It's simply a somewhat different version of the War of 1812, in which the Cherokees have a much more hopeful future. I'm cynically guessing that 90% of American high school students wouldn't be able to name even one of its deviations from history after reading it.
In spite of the title, all the events are set in 1814 and 1815, from the Battle of Horseshoe Bend through a rather different Battle of New Orleans. While Flint states in the afterword that his main purpose was to explore a history that averted the Trail of Tears, the novel focuses chiefly on battles. They're mostly well-written, letting characters be heroic without being unrealistic. But this doesn't leave much space to learn about the Indian tribes. No doubt the consequences are further spelled out in the sequel, 1824: The Arkansas War.
Flint presents some interesting characters, from major historical figures such as Andrew Jackson and James Madison to others who are invented or based on brief notes in histories. He runs into a problem for which there may be no good solution; there's effectively a literary taboo on characters who hold horribly racist ideas but otherwise are good people. What we understand today as racism had wide currency then, but if an author portrayed otherwise admirable racists, he'd be accused of portraying racism attractively. As a result, the black characters have a much easier time of it than they would have in real life. Jackson even gives one a battlefield commission.
Flint does overwrite at times, and the combination of the subject matter and style occasionally reminded me of James Fenimore Cooper:
Startled, Tiana tore her eyes away and saw that the Chickasaw whom James had sent into the river was now swimming toward her.
The half grin, half snarl on his painted face would have been enough to make clear his intentions. Even if he hadn't had his knife clenched between his teeth so that his hands would be free, allowing him to swim more quickly.
Mark Twain would certainly have asked how you manage a half grin, half snarl while holding a knife in your teeth, as well as objecting to the use of a period to separate a subordinate clause.
If you're a fan of alternate military history, you've probably already read 1812. I enjoyed it, but it didn't grab me enough to make me get the sequel.