You're probably hearing this for the umpteenth time, but here I say it again, if you liked Portal you'll like The Turing Test as well.
The gameplay is very similar, yes. You have a special gun and you solve puzzles with it and go from one room to the next.

But what is interesting about this game is its premise.
You're on Jupiter's moon, Europa, and the ground team is missing. You wake up from your cryogenic sleep as Ava and you're sent by T.O.M. (the AI) to the ground station to find the team. As you pass through each room, you get more and more information about what happened there.
Right from the start, the game presents you with a question - If we build machines with an advanced AI that can mimic human behavior, would that mean they can think and feel just like us? Would they be considered alive or conscious just like us?
And whether machines could have consciousness or not, how would that affect our human society? And how do we even determine if something has consciousness or not?
The game presents many points on either side of the argument throughout.
It somewhat reminded me of the anime Time of Eve[www.anime-planet.com].
(I believe you will have to read all the notes and stuff in the game to really appreciate this)

Now yes, this game isn't as big as Portal.
It's not as long as Portal. The puzzles are easier. And GLaDOS could eat TOM for her breakfast.
But as a standalone game, I did not find it lacking. I enjoyed it in fact.
My friend calls it 'Portal - Lite' and I feel that's pretty accurate.

Also, you get 100% achievements when you complete the story plus 7 optional levels (which aren't that difficult either).

PS. I received this as a gift from a friend.