If you played and enjoyed Portal series then you'll like this style of game. Compared to the portal series, I found Magrunner to have more challenging puzzles while Portal had better writing, but only slightly better. Magrunner does a great job building the atmosphere. Where else will you be expected to outrun a monster from R'lyeh while solving a magnetic puzzle? Having Cthulhu stare you down while trying to work the puzzles can be unnerving. This game is well worth the price. If they make a sequel I will pre-order without question.
I've played all the Overlord games, even the Wii one. Overlord does a great job of putting you in the seat of the bad guy for a change. I especially liked that you can choose to be bad or really bad :P And the minions are just adorable in an evil sort of way.