Okey, first of all there is a major issue with this game with the way it works and the fix is here: http://forums.steampowered.com/forums/showthread.php?t=1344121
Now, the game itself is a lot of fun! I've not played too far into it, but it reminds me of Lego Batman 2. It has many of the same features such as Golden Bricks, Students in Peril (with batman it was citizens, which fits better as they really were in peril) and being a large open world where you ttravel mission to mission or spend most of your time unlocking new secrets.
Instead of parts, you gain parts of the Hogwarts' crest to gain extra peices and you can unlock new students which may have interesting powers that will help you to unlock all the extras. This one doesn't have talking which makes me think it was made before Batman 2. Also, stud collecting in missions is a lot harder. I havn't completed a single mission yet where I filled up the stud meter.
A very addictive game and I highly recommend it if you're a fan of the other Lego games.