Let's just get this out of the way: Yes, Quantum Conundrum is a first-person puzzler, just like Portal. Yes, it was designed by Kim Swift, the project lead on Portal. And yes, it shares some of Portal's core traits: there's a physics-altering arm device, a goofy omniscient narrator, and an alarming number of buttons that need to be pushed.
But Quantum Conundrum crawls out from its spiritual predecessor's mighty shadow and stands, triumphant, as a game that's unique, raw, and brilliant in many ways. Finally, Portal has a worthy rival. Here's Quantum Conundrum in a nutshell: You're a little boy, age 8 or 10 or something unimportant (since your avatar doesn't talk or do much of anything), and you're visiting your eccentric scientist uncle at his eccentric scientist mansion. Just as you get there, the power goes out. Your uncle, Professor Fitz Quadwrangle, says something about being trapped in another dimension. Asks you to rescue him.
So you pick up uncle Quadwrangle's Interdimensional Shift Device, a glove that you can use to manipulate the objects around you by shifting any given room into one of four different physical "dimensions." Your job is to use these dimensions to solve puzzles throughout the mansion and restore the power so you can figure out just where the hell Quadwrangle disappeared to.