It is. MotB doesn't change or replace anything from the OC.

Is it true that Neverwinter Nights 2 is linear compared to first game and there is no exploration? Can the same be said about expansions?

Yes the NWN 2 OC is very linear, and while there are some sidequests, there isn't much in the way of exploration.
MotB is linear too, but you have more freedom to explore, and the story is excellent, so its linearity isn't such a big deal.
Mystery of Westgate is fairly linear as well, but you do have a big city to explore.

OTOH, Storm of Zehir is all about exploration, and if you really like open-ended games, it's well worth it.

uhm think im gonne try storm of zehir then

If you are judging based on linearity, I think you are making a mistake.....a game can be non-linear and be a complete piece of boring crap. Case in point, I never liked games like those from Elder Scrolls because of the non-linearity. It feels like dallying around aimlessly, with no purpose. I actually prefer more linearity. Must be because my favourite games many years ago were games like Zelda or the old Final Fantasy 7. But hey, your choice of course. Personally I am loving NWN2 Mysteries of Westgate to start with. Mask of Betrayer started with some pretty difficult battles so I'll give it a rest, I need to learn more about the battle system.

Im sharing your tought about that strangely I have bought the eldar scrolls games but only playing for a quater time of it I quit it, Because i end up wandering aimisly exploring every inch.

I've yet to complete and of the single player campaigns, but from my experience with NWN2 OC, it was, well, boring. I can't speak for MotB or SoZ. However, I find that the game has endless possibility with all the custom content out there, including new classes, races, creatures, modules, persistent worlds, etc. I've not played many games since NWN2 came out because I spend a good share of my time with it, mostly in the toolset.

NWN2's OC is a bit lame, but not too bad, and Mask of the Betrayer is amazing. Many have, and rightly so, called it the last great CRPG. Personally I do think Dragon Age: Origins is pretty good, so its not the last, but there are definitely few like it being made that are worth the money (or even playing). The game remains buggy, but its nothing serious, and there is lots of fan made campaigns.

In my opinion MotB is worth $20 by itself. To get all of that for $15 is like Christmas.

bought it immediately upon seeing the offer. waited and waited for the retail Neverwinter Complete, but nothing materialized. i think its worth it considering its now on GoG and fully updated.

Building is altogether more work in NWN2. The toolset has a steeper learning curve than in NWN1. The change from outdoor tilesets to walkmeshes, though it adds a great deal more control and realism, makes building an outdoor area from scratch take much longer. The scripting functions in NWN2 are greatly reduced from NWN1. Updates to NWN1 kept adding and adding functions, giving scripters more and more tools to work with, but only the most basic set of these was ported to NWN2.

The Elder Scrolls games bored me out of my skull. Fallout 3 was a bit better but again, bored me to tears. Like you, I never completed any. The problem with these games other than the feeling of no purpose, is the complete lack of humour. The main character and party members are always serious and boring. In all the NWN and NWN2 games this is well taken care of. In NWN Hotu I had a party member Deekin and it was really cool. In all these games I can always choose to reply with a funny ass comment. I like that, it makes the game more emotional.