Dipping back into the world of Harry Potter was never going to be an easy task. The world is already so rich with characters and events that it is hard to see how you could deviate from the known cannon.
A prequel is an obvious route, but making an entire film of of what is essentially a very slim grimoire of beasts from the wizarding world could be seen as an even taller order (just think about what they did with The Hobbit and that was more of a rounded story).
Being a fan of HP in the first place I was always going to be excited about new additions to the universe. And let me say that this did not disappoint!