After hearing several positive reviews and that even Stephen King himself loved the movie, I just had to watch it. But I was a bit disappointed tbh. It tries way too hard to be the scariest movie of all time, which eventually just results in it not being scary at all and me just sitting there, thinking "Okay, Pennywise, we got it, you're scary, next scene, please." Some scenes were also changed compared to the book, some were sadly left out completely. But I can forgive that. That book is over 1,000 pages long, that's a lot to put into just two movies.
On a positive note, the kids were really great, just like in the book. Those actors were simply fantastic.
Ironically, all the stuff with the Alien was what I least liked about it. The other stuff where Michael Fassbender pisses around with genetic experiments and talks philosophy with his twin was way more interesting to me. There's already a perfectly good movie about an Alien chasing people through corridors. It's called Alien.