The American Bicentennial series by John Jakes (8 volumes, later renamed “The Kent Family Chronicles”).

They were published in the mid-to-late 1970’s when I was in high school; I grabbed each new one as it was published.

Wait, I just realized I might be misremembering – I think volumes 1-3 were a box-set birthday present. But I did buy all of the others as soon as they came out.

I did the same thing! A friend recommended it to me; I accidentally picked up the abridged version. When we were discussing it after I read it, she mentioned several parts where I was like “Wait, what? I don’t remember that at all!”

Eventually I found out it was abridged, and picked up the complete version and read it right away. It was so much better! I was legitimately furious with the publisher of the abridgement – they didn’t just trim excessive bits of prose or redundant text; they just cut out entire sections indiscriminately, leaving big plot disconnects and a lot of unanswered questions.