Honestly, why all the hate?? Its a good game and great for potter lovers.
You start out at a visually pleasing representation of the burrow, you fly around a bit through the country side with Ginny for a bit of fun, it is these kind of additional sequences that I really enjoy in the game, yes they are not mentioned in the books however they all seem entirely feesable and complement JK Rowling's original plot nicely, but i'm just getting to that.
When you arrive at Hogwarts theres exploration to be done around the castle engaging in various tasks such as potion making, quidditch and most frequently, dueling. While carrying out your own free roaming of an accurate representation of the castle and grounds, you instructed by various characters to go to x y or z if you choose to follow what they have to say you will move along the plot through various ways, dissapointingly the main way is just a cut scene, but other times you can really interact with the story; for example, duelling Malfoy in the bathroom, duelling Bellatrix and Fenrir at the burrow or brewing a potion to cure poisoned Ron.
The fact that alot of the original cast are back to voice there characters the whole experience feels immersive and fresh, for example hearing Rupert Grint blurt out a couple of comical moments with different lines to those he used in the film is a nice addition.
If you enjoy collecting trophies then the games life span can easily be from 20-40 hours, it's not perfect but its great to feel like a wizard and experience the great series in an alternate way, considering you can grab this game for under a tenner off amazon its definetly worth it if your a potter lover like myself.