I did not like the first Magnetic Scrolls game, The Pawn, at all. It was juvenile, and the puzzles were unfair.
Guild of Thieves is much better; it's still unfair at times, but not so much, and the juvenilia have been cut back.
You play a thief who has to steal a large number of treasures from a castle and its environs. It's a very Zork-like setting. The map felt large at first, but eventually it was easy to picture it all.
There are treasures absolutely everywhere. It's easy to find several treasures, but I doubt anyone's found all of them on their own. Magnetic Scrolls aren't know for their fairness, anyway, but you can get a lot of enjoyment out of this game right from the getgo.