I don't review games on google often, but this is a game that, after a solid 10 hours with it, I can overwhelming recommend this game. Now, it does have a bit of lag and frame drop, but it takes very little away from the core gameplay.
The world is expanded upon from the first one, but knowledge of the first one isn't required.
The platforming is solid and never feels what you'd call "unfair", as the controls are very responsive. The combat is the same as it was in the previous game, which I have zero problem with, and expands on psychic abilities. The combat does feel more fluid, and gives you different ways to expand the abilities.
I won't speak too much to the story but the character development and way it addresses psychological issues is groundbreaking in a way that streamlines it for everyone and you can walk away with having learned something, even if you didn't mean to. But it comes with a zaniness that Double Fine is known for, especially within Psychonauts.
This game is a game of the year for me, and frankly, I can't remember the last time I had such fun with a game.