LOTR:BFME II is an excellent addition to its very solid predecessor. The style of the BFME game is much more along the lines of Command and Conquer: Generals than that of Warcraft 3 or Starcraft. Units are large, but relatively fragile. For instance, a swift cavalry attack can wipe out a unit of archers nearly completely in the first foray. What this leads to is a fast pace, almost frenetic battle, and the need for reinforcements is constant. The different factions contain similar units, but they all have very different play-styles. The Goblins are fast, fast producing, cheap and weak, whereas Isengard produces heavy armored Uruks and powerful Warg riders, only slower and with higher resource costs.
There is less "micro-management" than in some RTS games, notably Rise of Nations or Age of Empires, and the focus is solely on creating large armies fast with extreme amounts of devastation.
The best new addition in BFME II is the hero creator, allowing you to fashion your own Uber-Unit, granting it powers from a rather long power-tree. These hero units are amazingly strong, turning the tide of battle in an instant.
Some reviewers may disagree, but my favorite aspects of the game are the Faction powers. These faction powers are gained through "leveling" up your faction in combat. They allow you to summon allies, boost resource generation, heal your units, or eventually create a flood (ala Arwen in Fellowship) or summon the Balrog. The end powers can be the Deus ex Machina that turns a defeat magically into a win, if deployed correctly.
All in all LOTR:BFME II is a solid RTS, faced paced, bloody, with all the epic qualities of the movies. If you love the movies and enjoy a good clean fight, then you should enjoy BFME II.