A faithful adaptation to the book, not a remake of the 1990 tv miniseries.

Rating: 9/10 (21 September 2019)

Here is my lenghy, in-depth review of Stephen King's 'It.' This is mainly for those who have read the book, or those who have seen the film. Or maybe those who are just curious.
I'll just start by saying the I absolutely loved I've read the book six or seven times, and I was thoroughly pleased. I'll get into the changes and differences later, but all-in-all, it's a fairly faithful to the source material, captures the heart of the children's friendship, and is absolutely terrifying.
My thoughts on the 1990 Made-for-TV version:
This blew that version completely away. Many people look at that adaptation with fondness. I'm not sure why, because the TV version is pretty bad. While it is somewhat faithful to the book, it's cheaply made and poorly directed with extremely mediocre cinematography (the lighting and composition is cheap.) Not to the mention the effects are pretty bad, but that is due to the technology available at the time, not due to a lack of skill on the filmmaker's part. And since it was a network television presentation from three decades ago, it just wasn't scary. Which brings us to the most important part: Pennywise the Dancing Clown.
Tim Curry vs Bill Skarsgard:
Everybody loves Tim Curry, and rightfully so. His performance as Pennywise was what made the TV version. He stole the show, as the saying goes. He played the role with delightful, over-the-top madness. But the thing is, he's not scary. He's funny and entertaining. He's endearing. He serves the correct purpose to the story, but the audience wants to see him when he appears. He's really more of a mascot than a villain.
Bill Skarsgard's performance, on the other hand, is the embodiment terror. His other-worldly body language, masterfully timed head movements, bone-chilling facial expressions (behind full clown makeup, I might add), his smile that quickly changes from joy to terror, his eyes, and his voice all sends chills down your spine. Granted, much of this performance was aided by special effects, but it's still Bill at the core driving it.
Tim Curry deserves the respect, but Bill Skarsgard is the nightmare that feeds on children's fears. Tim is not.
The rest of the cast:
The casting is perfect. Everyone from the Losers Club is lifted straight from Stephen King's pages, right down to their physical details. Henry Bowers and his gang are perfectly cast as well. Even minor characters, like the Pharmacist, Eddie's mother, and Beverly's father contain the exact details described in the book.
Directing and Cinematography:
This film is masterfully directed. Every shot serves a purpose. Every frame is filled with so much detail, some details that the book lovers will pick up on, other details that are there for symbolism purposes. Other details that foreshadow the sequel. There is so much going on in the background of every scene that warrants multiple viewings to consume it all.
The cinematography is sheer perfection. There are subtle things happening that show the tremendous skill of the DP (Korean cinematographer Chung-hoon Chung, best known for 'Oldboy.')The lighting when the friends are together compared to when they are apart, for example.
Setting the film in the 1980s:
There are some people who whine when a film is not exactly like the book. These people are pretentious idiots who think they are displaying superiority with their 'the book is SO much better' attitude that annoy me to no end. Films cannot be exact replicas to the book. They are different mediums. Now that I've gotten that out of the way, let's get on with it (here's where the majority of the spoilers will take place.)
The film focuses only on the children, and leaves the adult versions of the characters out entirely (the sequel tells that part of the story.) The biggest change is setting it in the late '80s instead of the late '50s.
There are some who say they were just jumping on the success of 'Stranger Things,' but this is not possible, as the film was already written and well into pre-production before 'Stranger Things' was even a thing, and the production of 'It' began immediately after 'Stranger Things' wrapped. That is just coincidence.
The time-change setting did not bother me. It was still a time when kids would care-freely play together without helicopter parenting (side note: Eddie Kaspbrak's over-bearing, over-protective mother represents pretty much what all parents have become now.) So much of the sociological elements of the '50s worked just fine in a later time period. If it had taken place today, the kids would be all inside staring at their phones, and there would be no story to tell.
The time setting did require some of the horror elements to be changed. In the book, Pennywise tormented the kids by using many of the iconic 1950s movie monsters, such as The Mummy, The Werewolf, and the Creature from the Black Lagoon. This does not work in an updated time period, as those monsters were quaint by then, so some changes happened. Bill's haunting by Georgie and Eddie's leper remain, as does Beverly's bathroom scene (one of the most memorable scenes in the film, and even more disgusting than the book described.) Ben's mummy makes a very brief appearance.
The disappointing changes for me revolves around Stanley. In the film he is afraid of an odd painting of a woman, and she comes to life to pursue him. In the book, his fear of drowning is much more effective. I so wish I could have seen the scene in the Standpipe where he is chased by the bloated, drowned corpses of children. Why that was changed is a mystery to me, and unnecessary, as the passage described in the book was quite effective. The Standpipe does make an appearance in the film, and as a book fan I appreciated seeing it.
With these changes also came changes in the way the Losers Club battled It. Something that was completely lost in the film is how the kids used what they believed could defeat the monster, and it worked because it made them fearless. So the silver slugs they made are gone. Also, in the book Eddie uses his asthma inhaler to repel Pennywise, simply because he believed it would. There is a particular scene where I was anticipating it to happen, as it was the right opportunuty, but it did not.
Changes to the characters:
The only character changes made were with Mike Hanlon and Ben Hanscom, but they were rather minor. Mike's parents are dead in the film and he is raised by his grandfather, and I'm not sure why (unless I'm remembering the book wrong it's been a good seven or eight years since I last read it.) Also, Mike Hanlon was the town historian, not Ben. He was the one that pieced Derry's history together and figured out the patterns in great detail. In the book, it was the adult Mike who is the conduit of all this information to the reader. In this film, there is no adult Mike, and the viewer still needs the exposition. So this role was given to the child Ben, which does make sense as he spends a great deal of time in the town library. However, Ben's interest in architecture and engineering prowess is missing, which is a character trait that's important to his adult counterpart.
Henry Bowers:
As for Henry and his gang, they are all portrayed well. With the restraints of a film's run time, a lot about them is lost, which is unfortunate. Henry and his gang are a constant threat to the Losers Club, but in the movie they just show up a few times. An odd change is made that his father is a police officer instead of a farmer. Why the change? It makes no sense, unless it was some leftist 'cops are bullies' message that was being shoe-horned into the film. If so, that is unfortunate. Regardless, it was unnecessary.
The rock battle at the Barrens takes place, but the retaliation does not. It is Henry that breaks Eddie's arm in the book, but in the film the break happens when Eddie falls through the floor of 21 Neibolt Street (more on that later.)
As for the other members of Henry's gang, the viewer never learns about Patrick Hockstetter's sinister and twisted 'activities,' and he is killed without the viewer ever knowing anything about him. Belch and Vic are there, but disappear from the film with no explanation (a deleted scene does explain this.) In the book, they join Henry's hunt into the sewers after the Losers Club, and Henry witnesses their murder by It, which further drives him mad.
In the book, Henry is blamed for the murdered children, and is institutionalized after being declared insane, driven that way by his bully father and Pennywise's manipulation. His insanity is touched on in the film but not adequately developed, and the important plot point that Henry Bowers is convicted for Betty and Patrick's murder is left out entirely.
21 Neibolt Street and The Barrens:
As for 21 Neibolt Street, the house is portrayed perfectly. A good deal of the film takes place at the house and beneath it. Much of the Barrens is removed, though. The Barrens is an important part of the book, and it should have also been so on the film. The Barrens was where the Losers Club hung out. It was where they bonded, where they escaped into their world of childhood fun and friendship, away from the adults, away from Henry. It was where they felt safe. One of this is retained in the film. The kid's emotional and physical connection to the Barrens is also what made the rock battle such an important triumph for the reader. They claim territory and drive Henry away. In the movie, those emotional stakes just aren't there.
The Final Confrontation:
There is much that is changed here. Beverly is snatched by Pennywise, and he forces her to stare into the deadlights (a phrase that isn't even mentioned in the film, but is mentioned in the sequel), placing her into a catatonic state. Her friends then have to come rescue her. My first thought is that it turns her into the 'damsel in distress' cliche, which does not make sense, as she is such a strong character, the bravest character i