Read this in a day or two and really enjoyed it. But some will not. So fair warning: since Harry Potter and the Cursed Child is actually a play, you'll want to read it as such and imagine the story unfolding on stage. Caution: quite a few (too many?) scene changes. Just be forewarned and read the play for what it is - an extended telling of all that we know and love about Harry and Voldemort, but featuring "TNG."
If you keep that in mind, then it's a nice revisiting of the HP canon, a trip down memory lane (and into Godric's Hollow). In fact, it's kind of like an homage to the original series while introducing another related storyline. Sort of what Star Wars Episode 7 did for the original 3 movies. So if you want to immerse yourself in Pottermore, then this offering from J.K. Rowling (and company) serves that purpose well.
PS Subscribe to my sf/f newsletter and receive an e-book as a thank you gift.