IT Chapter Two - the followup and conclusion to 2017's record-setting smash, IT - has gotten a lot of attention for its 169-minute length. That's more than a half-hour longer than its predecessor and just a few minutes shy of Avengers: Endgame's infamous runtime. Then again, it was adapted from a three-pound, 1,138-page paperback, so no matter how long the big-screen version wound up being, a lot of material was inevitably getting altered, rearranged, or chopped out altogether. It's the nature of the beast.
But just how much creative license did director Andy Muschietti and screenwriter Gary Dauberman take with their second installment? Quite a bit, as it turns out. From Mike's revitalized role to Richie's deepest fear, from Derry's destiny to the reasons for Stanley Uris's absence, Chapter Two offers its own interpretation of one of Stephen King's most epic stories.
Henry Bowers, perpetual antagonist of the Losers’ Club, escapes from his asylum - with Pennywise's assistance - in both the book and the movie. In both, he targets a number of the Losers. In the book, he gets the jump on Mike, striking him badly enough that he ends up in the hospital. Afterward, Henry heads to the Derry Town House, finds Eddie’s room, and breaks his arm - echoing Eddie's broken arm when they faced Pennywise as kids - before Eddie manages to slay Henry with a broken bottle.
In the movie, Henry strikes Eddie first, jabbing him in the cheek instead of breaking his arm, and then escapes. He goes after Mike second, but is slain by Richie before doing much harm.
The movie version of IT makes a big fuss about the Losers needing to wander around town looking for personal totems of their past - totems they are then supposed to use in the Ritual of Chüd to seal Pennywise away.
In the book, there are no totems. After the meeting at the Jade of the Orient restaurant, Mike instructs the Losers to just walk the town alone to help them get their memories from the summer of 1957 back.
Pennywise’s ancient fall to Earth millions of years in the past remains mostly intact between the book and film versions of the story. The big difference comes with who actually sees it happen - and how. In the movie, we learn that Mike met a Native tribe outside of town who were able to give him a vision of IT's arrival thanks to a hallucinatory root. Mike gives the root to Bill after he arrives in Derry to show him the same vision - and to make him understand what must be done.
In the book, the Losers see Pennywise's arrival as kids. They decide to turn their clubhouse into a temporary smoke hut to try conjure a vision. They all start in the hut, but nearly everyone bails before receiving a vision. Only Mike and Richie stay long enough to see how the monster first arrived in the place that would be Derry.
This is a small change, and it's one that makes a lot of sense with the modernized take on the story. In the book, Richie is a successful radio DJ in LA who turned his ability for "voices" and impressions into a decent amount of fame.
In the movie, Richie is a standup comedian - one successful enough that he gets recognized in restaurants from time to time.