Realistic, immersive, great RTS, adds fun new maps and scenarios to the already great Total War game.
If you are interested in any particular time in history mention, or any of the cultures involved Kingdoms will provide you with several more hours of game play. The more isolated campaigns will provide a more fulfilling experience for players who may be interested in those factions, and the game still provides a challenge for a player trying to dominate the entire map, despite the smaller scale.
The bread and butter still stay with the Kingdoms expansion. None of the game mechanics have changed, and the visuals are just as spectacular as they were in Medieval 2. The required specs still remain the same, which means you wont need to upgrade to play this game; however that also means that more units involved in a battle can still bog down performance, even on higher end machines, so I would recommend lower some of the video settings and maybe setting the unit scale to low.
For a fan of Medieval 2 the Total War Kingdoms expansion provides a worthwhile gaming experience that provides a more immersive look at some more isolated instances of the Medieval 2.