Napoleon's exploits are a flimsy cover for the worst total war to date.
You primarily follow the exploits of Napoleon as he lives out his ambitious career from revolutionary to emperor. The game starts with a few short campaigns in Italy and Egypt/Jerusalem, but eventually goes into the traditional 'conquer Europe' scheme of things. The meat and potatoes of Napoleon is the relatively familiar process of conquering Europe in its entirety against four other major nations (Russia, England, Austria and Prussia) and a handful of nation-states. The problem with this 'plot' is that the Total war series is at its best when it isn't trying to be a plot. The last time the total war series followed a historical leader (Alexander the Great), it wasn't a terribly impressive experience. I can't speak for the millions of fans out there, but my favorite parts of total war series are watching my empire grow in size and scale.
Total war normally blends a lovely mixture of warfare, empire building, espionage and culture/religion into a mix that feels like a believable conquest of your neighbors. It uses historically accurate units, buildings and figures to give you a jumping off point for your own chapter in white-washing of history. Napoleon does away with most of the religion in game (it exists but you can't convert people in your empire), as well as most of the economy and espionage aspect. They condensed most of it down to make way for the militaristic tug of war you'll be doing with your neighbors. You build ports, roads and factories but it feels like going through a rhythm to simulate industrialization.
If you don't feel like being French then you can play a coalition campaign and try to conquer everything as one of the other four powers of the time (or just play empire). No matter what coalition you play as though, don't anger France (so in other words, just play as Prussia). Napoleon's name is on the title, so whenever you face him or one of his invulnerable generals you will certainly lose (especially if you autoresolve). It then becomes a game of 'see how long your empire will last against an endless army'. Napoleon is almost always guarded by an entire army of elite soldiers, and the only time I had a chance against him was when my forces outnumbered him 5 to 1. If the developers expected you to make an alliance with the world and stop him, then they hoped wrong. If you focus too heavily on economics (ie, you build ports and roads instead of armies) then you are basically setting yourself up for invasion from all possible sides. This doesn't make sense seeing as how you are SUPPOSED to ally with these nations and stop Napoleon. Focusing on armies leaves you a destitute nation that's vulnerable to destruction in another way. There's a balance to strike here, but it is so tedious that it sucks most of the joy from empire building away.
The graphics suffers from a guilty case of 'Left 4 Dead 2 syndrome', in that the developers are essentially billing its fans for a very similar game with minor graphical tweaks. The map does look better than empire though. Cities look less like 4 buildings, battles take place in towns now and the map looks slightly better. The game looks better.
The audio doesn't sound better though. The game uses a lot of recycled sound effects, such as the turn-ending sound and the prompt/attack sounds. In a similar capacity, it borrows heavily from the old interface; research, diplomacy and government are all nearly identical to the previous game. The music also sounds strange; it is era-accurate classical that feels off. A single piano drums in the background somberly to almost make you feel guilty about the blood you are helping shed.
Napoleon acts largely as a break between Empire (which a large chunk of fans understandably did not like) and Shogun 2. It begs repeating that creative is abusing their franchise by making near annual releases with minor tweaks, like this is a Madden style game. Hopefully Shogun 2 will break the pattern, but damage has been done here. Napoleon: Total war hides in the shadow of better games in the series, and the 'conquer Europe' routine feels a little stagnated after the support elements have been reduced.