This post (specifically answers from /u/erictotalitarian and /u/Borimi) seems to answer your question:
Having read it myself, I'll add that it's definitely not something I'd cite as a reference for anything, but it's an excellent, if flawed, narrative history of the war. Leaving aside more administrative-type issues like his lack of proper sourcing or training as a historian, its biggest flaws are Foote's fairly significant Southern bias. He avoids probably the greatest potential pitfall of Southern apologism, stating openly from the start that the South seceded first and foremost over slavery, and he consistently comes back to that point whenever the subject of the South trying to gain international recognition comes up. However, despite not shying away from the topic of slavery itself, he generally ignores the slaves themselves, only ever really portraying them as faceless caricatures. In fact, the biggest criticisms of his work tend to come from that angle. He's uncomfortably sympathetic towards Nathan Bedford Forrest.
Despite its flaws, however, it does have its value for understanding the Southern perspective of the war. While slavery is hardly an admirable cause, Foote's sympathetic focus on the South does tend to provide an understanding of how and why so many Southerners were willing to fight in the first place. It absolutely shouldn't be the only contribution to someone's understanding of the war, but it can be a valuable one.