I think Foote's trilogy is one of the true greats in terms of Civil War scholarship, and I frequently recommend it to newbies who are interested in studying the Civil War. I really think there's no better way to wrap your head around the whole thing, and in an entertaining way.
That said, there is one major problem with citing Foote - as
@MaryDee noted above, the lack of his own citations in terms of footnotes and endnotes. Even the most brilliant, respected historian should not expect us to just take his or her word for everything they write. We need to see where they got the information from. If we can't see that, or if the citations are sloppy or just plain wrong, then it really has no value
in an argument or a debate. But that doesn't mean it might not still have tremendous value outside of arguments or debates.
For me, the best authors are those who correctly cite lots of primary sources to support their claims. It's the primary sources that I really find fascinating and often full of all kinds of useful information that the historian doesn't have time or room to include in their work. Furthermore, if we can go directly to the primary source we remove all biases of the historian from the equation. Of course that's not to say that the primary source doesn't have its own bias, but at least that bias is part of the time period we're studying, and not noise that's been introduced in some later time period.