I didn't like it that much
Whenever I watch a horror movie, I'd like them to have somewhat constant spooky atmosphere, so that it's not that clear when something might actually happen. But in this, the scenes were too obvious imo, so you were always prepared for what might happen.
I understand that in horror movies people are usually stupid, so that they get themselves in bad situation. In this movie, they were even more so stupid, especially in a few scenes.
There were also a bit inconsistencies on how "it" acted and at least one (maybe not so important) poorly explained plot thing (TV show). I mean these might have been explained better in the book, but I'm an uncivilized barbarian...
I would explain these a bit more in detail, but I'm afraid it would spoil a bit too much