When people talk about games as being a hidden gem...this is the type of game they're talking about.
There is a fine line between puzzle games and adventure games. Games such as Myst are labeled as adventure/puzzle but it's nowhere near a true adventure game. Myst would be a puzzle game. Syberia is a real adventure game. I would label The Neverhood more on the puzzle side than adventure even though it has it's fair share of adventure. But it's all subjective I guess.
The unique thing about this game is it's made out of clay. You can stop reading right now and go buy the game...I mean how much more do you need to know? It's made out of clay! The fact that it's made out of clay brings the story and characters to life in a new and refreshing way that typical animation can't do. The different worlds/places are beautiful. The characters are funny and designed in a unique way. If you play this game and never laugh there's something wrong with you. The Characters are a riot. They have GREAT voice acting and awesome dialog.
The puzzles are just right. Not too hard..not too easy. You may need to look at a walk through a couple times but if you stay determined then you should be able to figure it out. I think what sets this apart from other puzzle games (besides the fact that it was done in clay) is that it has an immersive story. Usually games more on the adventure side have the great story but The Neverhood was able to incorporate a great story that will keep you captivated.
Also, you will get attached to the characters. This game has alot of aspects that an adventure game has but remains mostly a puzzle game. That's why it's hard for me to decide which of the line it's mostly belongs on.
Even if you don't like puzzle games such as Myst, Rhem, etc. You are sure to love this game. Unless you're gamespot...which apparently hates the game. If you're a gamer pick this game up...believe me, you won't be disappointed!