Somehow I wound up reading Thoreau instead of actual Civil War material. I don't even like him very much; he always sort of bugs me, with the ranting and the "simple life" in which someone else cooked his meals most of the time. So I'm trying to appreciate Thoreau better.
I read Civil Disobedience, in which he talks about his opposition to slavery and the Mexican War. He didn't approve of the American government, so he refused to pay poll taxes for several years. He figured that if everyone refused to support the government in wrong actions, it would have to give in. For his refusal to pay taxes, Thoreau was put in jail for a night. His aunt then paid the back taxes against his will, so he was released. A good deal of the essay talks about his night in prison and how much he liked it.
There's some good stuff in the essay. I like his maxim about the least government possible being the best kind. He expressed hopes that eventually a minimal government would give way to none at all, which seems a bit improbable.
I also read an essay about Slavery in Massachusetts, which was originally a speech castigating his fellow citizens for worrying about Nebraska when the Fugitive Slave Law was in effect right there in their own area. Another essay is a defense of John Brown, but I'm not done with it yet.
Then at the last minute, I read Lincoln's First Inaugural Address, which was largely designed to avoid a civil war. In it, he reiterates his opinion that a President has no right to abolish slavery (it had to be done by Constitutional amendment), and repeated over and over again that no one was going to attack the Southern states and that if they wanted a war, they would have to start it.