Here's another incredibly long recommendation from me :D

This game isn't just one of my favorite games of all time - It's also one of the best RPGs I've played and also the first western RPG I've laid eyes on. Lastly, I find it to be much, much, much, muuuch better than the original Knights of the Old Republic from BioWare. It takes the gameplay mechanics of its predecessor and improves upon them to a greater extent. There's no ridiculous level cap from the first game anymore either. Much more open freedom to build your character with the introduction of the Advanced Classes.
Lastly, the writing, story and characters are well-rounded and not drenched up in clichés like the first game. Knights of the Old Republic 2 throws the whole Light vs Dark concept into a bin and then dump it on the dark side of the moon.

In retrospect - The game basically views the Jedi & Sith from a broader perspective and then concludes "Hey, maybe they aren't so different after all". They both wear morning gowns for a living and carry wide coloured willie exstented swords as a means of defense or offense. Essentially, there is no good or evil in this game, just various shades of grey. This philosophy is something one would find in the game's characters, especially the enigmatic woman, Kreia. Most of the characters are incredibly complex, even the Han Solo-esque ones have a dark secret hiding in the closet.
There's no suave, secret, paragon of the universe response that will unlock their hidden feelings and open up to you. There's an interesting approval system, which I do consider a bit flawed but in terms of role-playing, it works. Once you've finally gotten to the heart of their character you'll unlock new abilities for the said characters. The best part: Even when you've gotten that far it still feels like you don't quite know everything there is to know about these characters.

I think it is best if I sum up the plot now -- The game takes place a few years after the events of the first game.

In classic Star Wars tradition, the Republic is on the verge of collapse alongside the Jedi... AGAIN. There are some tropes that Star Wars can never truly escape from I suppose. You play as an exiled Jedi... Knight? Master? Janitor? Whatever, the game is kinda vague about your previous ranking within the order - You've just returned to the known galaxy and thus missed out on the party of the first game -- I suppose this makes sense given that Star Wars doesn't seem to be restricted to one galaxy, but how the Exile have managed to NOT hear about the whole escapade in the first game is beyond me.. Guess she spent her time in a cave or a remote planet or something, ala Ben Kenobi. For some reason you find yourself onboard the ship of the Ebon Hawke, which people who've played the first game will recognize, and it has been badly damaged, explains a questionably-soothingly-female-voiced-sentient-AI as the tutorial begins.

You have the option of skipping this tutorial but it's probably best not to do it since it'll give you a better idea of what is going on and foreshadow danger to come. Not too long after your Exiled Jedi wakes up from her/his comatose sleep onboard an eerie space mining facility called Peragus. The whole place is mysteriously abandoned, and one of the only survivors seems to be an old woman named, Kreia. Like I mentioned she's an enigma and she seems to know a lot about you and the Force, so the next course of action is to figure out what has happened and get off the station. That pretty much sums up the beginning.

One of the other things I find that Kotor 2 does exceptionally well is that it allows the player to get easily integrated with the character of the Exile, despite her having an established background -- The well structured dialogue assignment paves way for role-playing a character who doesn't have a clue, as well as someone who's already familiar with the events of the first game. In addition to that - There's also the subtle choice of gender for the previous protagonist and selected occurences of the first game, without the use of an import system, in conversation with one of the characters. A smart way to build to connect both stories together as there'll be plenty of references.

So, I've talked a bit about what to expect from the characters, the story and gameplay -- Now I'd like to sum up some of the central themes. The game doesn't present itself as the "Save the world from the ancient evil" type of story. Instead, it sets itself up more as a personal story, about your protagonist and your followers. Every time you exit and enter your ship you'll usually find the party bantering with each other, alluding to a dark secret they are hiding or what have you. This is also brought to light in some of the story cutscenes, where Kreia will downright intimidate your crew by exposing their darkest secrets and have it consume them... Why? Because of The Exile. The Exile is unlike any Jedi or Sith and not because she drew the shortest stick, but because she did something in her past that none other could have done. Something that litterally draws the followers and Kreia alike, to the Exile, but one would have to play the game to understand. Most of the story is a lesson to the protagonist, and the player -- About the ideas of morality, and how being a nice & benevolent saint might not always be the right thing to do; Least of all being cruel and despicable.
Relying heavily on the Force is brought up as a sign of weakness, and that true strength comes from not needing it. All of this is dictated through the enemies you fight, the choices you make, the characters you meet and certainly through the character of Kreia. It's

KOTOR 2 is a story of self-realization, different shades of morality, confronting the past and learning from past mistakes to face the future. Knights of the Old Republic 2 gets a strong recommendation from me, simply for being unlike any other Star Wars game and with the Restoration Mod -- A much better game than BioWare's original Knights of the Old Republic! :)