Did not like it, have to read the book again to get rid of the bad feeling, here's why:

Rating: 2/10 (22 September 2019)

First of all, this is my first review here, and IT is the first movie that made me do the effort.
There is a simple reason for this: I am 41 years old man that read the book back at the age of the main characters and was captivated. Thriller, horror - all was good enough, but the genuine story and developing relationship between the kids was what bought me in then and now, and this books remains my favorite one till present. I remember being much surprised about how the kids thought the same way I did back then, I could connect to their problems, longings, fears and hopes. I have read it multiple times (easy 50+ times) till now, also as an adult, just going back into the growing relationships and feelings, and love and hope, true friendship - this always makes me feel good, a little sad (at the ending), but still in a good way.
This is why it was a must for me to see the adaptation of IT, and here I went to watch the first movie. It was bad enough (for the same reasons below), but I patiently waited for Chapter Two. However, where the first movie made wrong, the second movie progressed into disaster.
Going back to the movie, all set and casting (as visual looks, though, as acting I did not like - but it was mainly because of the script, in my thought) was really promising. But, all else went downhill, and this is what I mean (ATTENTION: spoilers ahead):

Where everything made sense in the book, including all efforts of IT to unsuccessfully kill all of the Losers, here nothing make sense in the movie. If you have not read the books, you simply cannot understand why IT does not kill them once and for all, but plays with them till eventually they kill IT. All IT's actions was ridiculous and meaningless, in most cases. Not even starting on SGI, enough said in other reviews (terribly overkill).

No growing connection and relationship between the characters, neither as kids nor as adults. Ben built the clubhouse ALONE before getting along with the rest of the kids (what a club house is this, if it is not made in the club?), the dam scene is deleted entirely (and this was exactly the Losers bonded together as a club), the Smoke ritual was made only by Mike and as an adult, the meeting as adults was soulless and tasteless in many occasions. I do not think the Club ever did anything meaningful together in the movie (except for the rock fight, which feels rushed and illogical, in the absence of the rest). Even the last collisions with IT were done individually (except the ridiculous end, but for this a bit below).

Henry Bowers (and the rest) role to drive the Losers together is completely missed, which made his participation into the movie completely unnecessary. In addition, while the book made it clear that killing Henry (which was much a victim of IT, as the rest of the kids anyway) was almost equally bad and helping IT, and though Henry did die in the book, no one of the Losers was actually aiming to kill him. This does not work in the movie - they split Henry's skull, and immediately continue to run jokes between themselves. Come on, guys, it does not make sense.

In the book Bill was the natural leader of the Losers, both as kid and adult. His motivation as a kid for avenging his brother's death grew into an wider understanding of the numerous deaths of kids throughout the years, which kept him going and leading the Losers ahead of the collision with IT. There is nothing like this in the movie, they even made Mike the leader of the group as adults (come on, Hollywood, how politically correct you need to be? One Afro-American in the group, and we need to make him the Leader to keep all satisfied?)

The letter from Stan Uris at the end was a lazy and stupid way to explain something, which should never need explanation. And beside this is completely not coherent with the book as far as Stan's motivation to kill himself. Pathetic.

Beverley visions of the future - useless, meaningless, stupid, at best.

The end collision with IT had some potential - and I would understand if they beat IT though love and some natural positive power, or whatever. But they did kill it through bullying IT - calling IT bad names, swearing at it... Come on, guys, I know it is very difficult to adapt the complicated ending in the book, but so same lame a try is too much.

Finally, one thing which really upset me off, was adding a home-sexual thing between Richie and Eddie. Where this came from, I will always wonder, and the only reason I did not go out of the theater at this stage was that this came as a fact at the very end of the movie. Again trying to be politically correct or what, I simply do not understand.

I can probably continue like this with a long list, but there is no need. As a resume, I do not think that anyone that enjoys the book (as I did) will ever like this adaptation, as it has very little (if any) of the book spirit and message into it.
For the ones that have not read the books (thus, not being able to connect the abyss of missing dots), probably it will not make much sense, but if you are into a following set of jump scares and overkill-SGI monsters, it might be watchable.
Finally, the mini-series of IT had their flaws, but they had a much better grasp of the book message and feeling, they had a heart and soul, and made me connect to the Losers, which is why I enjoyed watching them. Which is not something I can say for IT and IT Chapter Two.