If you don't know much about Napoleon, you'll probably enjoy it. If you do, you'll be frustrated at best and most likely disappointed and underwhelmed. If Gladiator is 98% fiction, this is around 70% fiction or at least cherry-picked to the point of fiction.
Napoleon is one of the most interesting humans to have walked the earth. His rise from a poor noble family and outsider in French military schools, to a leader of democracy, to a mastor propagandist, to an Emperor, to making a massive blunder in Russia gave the director a chance to leave the audience's feelings up to them to decide if he was a hero or a villain, which he was a bit of both. This movie clearly depicts him as a villain which I think ruined it for me more than anything. It sheds no light on his background, uses cherry-picked scenes, and ignores all of the amazing feats behind the scenes that led to his rise as the first man who EARNED it, not born into the monarchs.
It was a republic vs monarchs to begin with. This movie seems oddly pro-monarch yet anti-Empire. I'd have loved to see a movie that sets up his turn from republic to Empire and leading troops who loved him and fought for the Republic as he turned towards what he despised as a young captain, monarchy. This fell totally flat for me, but I can see how people wo don't know may enjoy it.