More specifically I'm interested in learning about the early colonies, and the subsequent American nation, in particular, the wars and political decisions that led to independence.
"Serious" herein meaning more depth than a simple look at the overall situation. I have plenty of books that talk about what happened at Lexington and Concord, but very few bother to detail why it happened, what led up to it, etc.
I suppose this is a general question for best reading material about US History in general, with a focus on pre-civil war.
I think you would be happy with the Oxford American History series. I think Crucible of War (7 Years War) is fantastic. Also, Taylor's American Colonies is good as well. Those are overviews. If you want more specific, then it gets down to whatever topic or event it is you are interested in.