There's a little ambiguity: Do you want a general history of the United States, like 1797-near the present (or starting further back)? Or a book that covers some part of US history, but does it very well? Or whatever?

I think that A People's History of the United States by Howard Zinn is a must read. It offers a post revisionist view on America dating all the way back to Columbus. It really is an eye opening book and a fantastic read.