I know there are lots of awesome books on US history, but which one is the best ...

My vote for a history that is both detailed and written at the level of the general reader would be the three volume series: "The American Experience" by James MacGregor Burns. The three books are titled The Vineyard of Liberty, The Workshop of Democracy, and The Crosswinds of Freedom.Burns makes meticulous reference to primary sources without getting bogged down in historiography (issues about sources, arguments between historians, etc.) instead of history (what actually happened, how, and why). He has no ideological ax to grind and no particular point of view that he tries to force-feed to the reader. The writing is clear, evocative, powerful, and easy to understand.And, for me, it is written at just the right level of detail for general history. There is enough nitty gritty to give the reader a real feel for the people, events, and circumstances of the times discussed, but not so much detail that only a serious historian would be interested. These books are emotionally involving without being emotionally manipulative, as well--Burns tells the story such that the writer gets out of the way, allowing the reader to look through a clear pane of glass into the past. I can think of no higher praise for a work of history.