Quite innovative in the Harry Potter game series: the all-expected breakthrough in the series.
To begin with, the enabling of multiple keys for different spells made it a more fun and engaging game, even going as far as to resemble a First-Person-Shooter. I was also able to CHOOSE my characters in each and every mission, also being a major improvement of a severe limitation with its 3 predecessors. As for the graphics, they were convincingly breathtaking too, undoubtedly when compared with the neo-puppetry I saw with regards to character animation in the very first game. Such creativity and imagination in this sparkled my interest further, and would have been so permanently, were it not for the rather confusing nature of its game-play. As with all innovation, this one had that one major flaw the others didn't have - in its confusing, even bureaucratic game-play.
The best instance of such confusion lay with its procurement of Shields. I mean, I was unable to complete some missions purely because some spells, such as Herbivicus. Such instances lead to an automatic exit of the mission, and hence after I learnt the spell, I forgot to come back and cast the spell to complete it (were it not for those online walkthroughs I used as an aid). It was a rather inefficient element within it, and for a moment I almost gave up playing the game, but in the end, I enjoyed it somewhat.
In conclusion, I would have rated this 9 out of 10 for its engaging animation, creativity and spells, but for its game-play I would definitely not. In fairness though, this was a definite improvement on its predecessors.