If you only intend to play the singleplayer and don't want to get involved with the mod community, then bluntly put, NWN1 is not for you. The Original Campaign for NWN was bland, boring, and predictable with mediocre gameplay and unimaginative design. Doesn't help that in NWN1 you only control one character and your companions are AI controlled (And pretty much useless!) so fights quickly tend to grow boring. There are some mods which have story that capitalize on the solo experience and do it extremely well, but Bioware themselves never really did it that well and overall the singleplayer just ends up feeling lonely and tedious. The reason for this is centered around the multiplayer, but I was never big into mp and the singleplayer ended up suffering.
That said the expansions are better and there are some amazing fan made campaigns out there for the game. Hordes of the Underdark was the best part of the first game as far as singleplayer is concerned, but it's still not very good when thrown up against even Bioware's other works. Still, not bad either, you could do worse.
Some fantastic mod campaigns though, easily my favorite part of the game and the reason I own 2 copies of NWN and its expansions. I've spent easily hundreds of hours playing NWN, less than a tenth of which was ever spent playing the content Bioware made. But then there are also some amazing campaigns for NWN2 and you didn't touch them, so I don't think you're much into that aspect.
As far as I'm concerned though the high point for the entire NWN series though was the first expansion pack for NWN2 called Mask of the Betrayer. Unlike everything else in the series, it's got a genuinely good plot, interesting characters, and a new take on the now-familiar Forgotten Realms setting.
And did I mention mods? There are some bloody brilliant ones out there for both NWN 1 and 2. Best part of the whole series, Mask of the Betrayer aside.