Even today this game stands out as a pure classic -- a sort of "does anything" game.
NWN is really several games in one. There's the original campaign and the expansions, the toolset, the multiplayer and a literal vault full of user-made 'modules', which is really a way of saying 'games'.
Out of the box, it's a good idea to start off with the OC to get to know the game. This is really the weak point of the game -- it's very long and caters to all sorts of playstyles, but at the same time it feels bland.
While it has a great pedigree (it's developed by the same team as Baldur's Gate), the way the story ended up is very weak and predictable with few plot twists. The role-playing isn't very deep and it's mostly a hack 'n' slasher. Interestingly enough, there is an original plot draught available on the web which is a lot more interesting but at the same time more complex.
There are several henchmen available to employ, but you don't get the feeling of a part, one of the major let downs of the OC. They're not particularly interesting, but they do their jobs. It really is more fun to play through in multiplayer.
By modern standards, the graphics aren't great. However, the engine itself is fairly good. It supports very high resolutions despite the fact that it was released 7 years ago and if you look at newer user-made content you'll realise that all that's really missing are bump maps and fancy effects. I personally like the look of NWN, and as the game has been very well supported by BioWare the engine is incredibly slick and solid. The only problem is that some elements of the interface are a little small on higher resolutions.
The original game looks a little generic but the expansions add more exotic tile-sets to the game. The soundtrack is also top-notch - the voice acting and sound effects are a little middle-of-the-road but Jeremy Soule (also known for "The Elder Scrolls") has written a wonderful score that accompanies the game really well.
While the character models don't look great, they are very varied and NPCs can be fully customised for your own modules. There's a wide variety of character races and classes from which to choose, and virtually infinite user-created hacks and add-ons.
As the game is based on Dungeons and Dragons 3rd edition, the combat is very mathematical and success is really based on how well you've built your character. There are a lot of spells and loads of ways to progress your character and all-in-all it's a good system that's been very well integrated.
You might choose to play as a large, insecure half-orc barbarian with a big mouth , a batty old elven wizard obsessed with his books, a sexy and persuasive female bard or any number of other character builds; it's really very varied and a lot of fun to experiment with different character options.
The main draw of NWN for many players is the Aurora toolset, which lets you create your own modules with great ease. Within about a week you'll be able to use it like a pro. The interface is very slick and pleasant to use, and it's possible to create stunning creations (Like Ossian's "Darkness Over Daggerford", Adam Miller's "Demon" and the renowned "Tortured Hearts" modules.)
Even better is the fact that you can take your modules online to play with friends. Even today there are thousands playing online every day, and the community is very much living. I can personally claim that the community are one of the most helpful and friendly on the entire internet.
The online aspect of the game plays very like the single-player version. It's very easy to get started and the interface works really well. My only gripe with it is that it can be hard to know what any specific module will be like if you're simply browsing through a fairly basic server browser.
There's full support for a Dungeon Master, and while I'm not a great DM I must say the inter face works really well. It's a lot of fun for both the DM and the players, as it can add a level of uncertainty and originality to a module that was designed a specific way. For instance, the DM might possess an NPC or spawn more monsters for the players to massacre.
Finally, there's a massive website called the NWNVault that's literally packed full of modules, tutorials, information and modifications. It's the perfect place to find something new to play among literally thousands of user-made modules. It's also worth notign that, unlike most games, pretty much all of the user-made content can be found on one truly stonking site.
All in all, this a stunning game. The only let-down is the Original Campaign which is a little dull (but perfectly okay), and with a wide variety of ways to play, a big community, very light system requirements and a tiny price tag there's no reason not to go for it!