For a spin-off, Fantastic Beasts seems pretty detached to the Potterverse. Apart from essentially connected to Grindelwald, it is a(mericanized) whole new whimsical world with its own terms and rules.
The storyline feels underdeveloped and crammed up, which is rather disappointing considering JKR writes the screenplay herself. She supposedly has plenty of time to tell more backstory since it will be made into a pentalogy!
But great thing is, you can see her signature writing and how good she creates the characters and how she builds their relationships. You’ll grow fond of the new gang once you get to know them.
The actors are well-cast, but there is only one scene stealer. By Merlin’s beard, doesn’t Colin Farrell look dapper in that overcoat?! The actual fantastic beast in the film. Rawr.