Goosebumps: HorrorLand puts you in the horror-themed amusement park run by monsters, and for the most part, the game does a decent job portraying that fact. While the graphics themselves aren't as crisp as some other 3D games on the system, they do a good enough job showing you what's going on. Your character looks okay during his closeups, but with the camera pulled back as far as it is while running around the park, many of the sharp angles from the low polygon count go away. Even the in-game cutscenes that occur during various parts in the game (typically when you first go into a new part of the park) end up looking okay - nothing spectacular, just okay.
Sound definitely feels appropriate. The speakers are constantly filled with music appropriate for the themed area you are in. For example, Carnival of Screams uses that (appropriately) eerie carny music. The sound effects are also mini-game appropriate. During the HorrorLand Derby, your ears are filled with the sounds of a horse race, while other games like the Calamity Canyon roller coaster have that distinct wooden coaster sound of a cart on tracks. For the most part, the sound adds just the right amount of atmosphere to the game to make it worthwhile. HorrorLand also uses voice acting for the cutscenes instead of having you read the story, which is always nice on the DS.