If you only choose to read one (challenging and sizable) resource on the American Civil War, this is the one. It won the Pulitzer, and although it is a large, serious piece of work, it is immensely readable. It begins with the Mexican-American War because that is where much of the Civil War’s military leadership is forged. It also makes it much more interesting to see whose fortunes rise, and whose fall (although these are, naturally, secondary to the issue of the war itself).
This is unquestionably the most thorough and accurate volume about America’s last righteous war. It requires a high level of literacy, but with that caveat, it is a surprisingly accessible narrative, from a man who documents everything and knows what he’s talking about.
One other thing: I find that in discussions about the Civil War (still referred to in much of the South as “the war between the states”), though it is long past, in some ways it isn’t over. Feelings are sometimes still surprisingly heated. And indeed, anyone who writes history is subjective, even if it is only by the facts they include (and which are emphasized); what sections or titles are named; and which generals are given the most air time. So though nobody is entirely objective, I think McPherson is the most reliable, knowledgeable, yet objective writer I’ve found yet.