CA have really pushed the limits of their engine in this revisit to the Sengoku Jidai period in Japan.
The game keeps a similar mechanic to that of the other games, but this time has severely improved the campaign ai.
The Campaign map is highly detailed, and is accurate to the time period, as is the castle building and recruiting system.
Each clan has specific bonuses, for example, the Oda having cheaper costing ashigaru that have better morale.
Also, because the campaign have better Ai, you are forced to take more care in how you use your turn, sometimes having to turn to diplomacy, which has also been improved by adding the likely reaction to your offers and demands.

The battle system is a bit more responsive, and the sea battles are a large improvement on the other games. Not to forget the multiplayer, which has been expanded upon to become another major part of the game.

At an average playthrough time at about 15+ hours,this game is well worth buying