AC III is a storydriven game where you have virtually no freedom, but a huge, fairly empty (yet good looking) world to roam around in and enjoy your lack of freedom. The story is set in stone, nothing you do can change it.. not even when you fail certain tasks.
The story within the animus is... entertaining at least, but the big plot of the series that started out so well is a piece of crap that will make you laugh. Combat is good looking, but very easy and gets old within the first act or so. The unlockables are generally a waste of time, especially the outfits as they are full of bugs and generally lack in visual quality. Getting new weapons and trinkets is easy, yet completely waste of money/time/effort. As I said, the game is piss easy all the way to the end even if you never upgrade anything. The game is actually so restricted that they might just as well had released it as a movie, as the players input is hardly needed in this game at all other than to move your character from cut-scene to cut-scene and perform incredibly obvious (sometimes really stupid) and easy tasks along the way. The action sequences where you have to push the right button at the right time is AWFUL to say the least, pathetic really, and the secondary objectives that pushes the player to do each quest a certain way down to the smallest detail is just damaging. Remaining undetected should be a no brainer for most people (Assassin...) but what the fuck does it matter if you kill three guys with a gun, two with a rope-arrow and five by pissing down their throats??? It's STUPID! If there was any shred of freedom left in this game, it would have been quite decent. Sadly, it's a hand holding shell of a game that might look good but once you played it you have no feeling of achievement other than having wasted several hours of your life.
Anyone able to follow the big quest marker will be able to finish this game, even if they have both their hands amputated. It's generally a piece of shit game, but a "must" playthrough for those who have played through the previous games.
The first AC game was great, lots of freedom during the plot kills the world was fairly "empty" still. ACII was very good, even though if more restricted as the world was more populated with things to do other than following the main quest. The next two games was entertaining, visually pleasing and also had some nice side quests. Revelations had a very annoying mini game called Tower Defense, but you could completely avoid it if you made sure your Anonymous meter never got past half. (thank god). All of them except the first rob you of freedom during main quest kills, the cut scenes makes sure it's a fucking timed event or similar rather than a well placed assassination like in the first game, this is the only reason the first game is incredibly much better than the sequels. For new gamers to the series I recommend starting at the first game, and if you fall off before finishing the series you would most likely HATE ACIII anyway. It's by far the worst game of the series... BY FAR!
PS. The naval combat was entertaining but also incredibly stupid and restricted. The game in general is full of potential, but the restrictions is killing the game.