*Spoilers Ahead*
If you like King's more recent Bill Hodge's Mr. Mercedes series, you'll love Stephen King's The Outsider. In fact, Holly Gibney makes a reprise in his book/TV show and shines as a character all on her own. The Outsider takes you into a crime that seems impossible, and as the investigation keeps going, the story keeps getting weirder and weirder.
It introduces us to a brutal murder and molestation of a child that a hiker finds in the woods. When eyewitness testimony and his fingerprints point to beloved baseball coach Terry Maitland, he is as surprised as can be. But even though detective Ralph Anderson has him arrested in front of his friends and family during a game, he is more than sure that he committed the crime. That is until a tape reveals that during the time of the murder he was at a teacher's conference in Cap City.
The investigation unravels from there and it challenges everything that Ralph and his investigating team thought that they knew about crime - until Holly shows up. If you read the Bill Hodges books, you would know that she ran into strange suspects like Brady Hartsfield before, so this situation was nothing new to her. By taking Holly's direction challenged the group, and it might have just been what they needed to get them on the right track.
The story takes several twists and turns and as it dives deeper into this strange world, we want to read and watch more. This is one of King's best modern books, as he makes his characters and situations feel so real you can actually see them happening. For everything that is close to the book in the HBO Max TV show, there are things that they adapted or added. The list below tells what they changed. I would highly recommend reading the book though as well, as I believe the book is even better than this strong ten-episode mini series that is just as addicting.
Main differences between the book and the show:
Andy's character
Andy was not a character in the book, so the whole love storyline between him and Holly never happened. I guess they added it there to ease all the dramatic tension and then again to build tension when he dies later on. It worked, as when you watch it as a show, it can be rather tense. But if you insert his character in the book, it would make as a rather dull read.
Derek's character
Derek is not dead in the novel. Instead, he is away at summer camp the entire time. I actually thought it was stupid given that there is no need to mention a character being away the entire time. It didn't seem to serve a purpose to me. In the show, however, him being dead gave it a new dimension in the Anderson's lives. It showed the grief that Ralph felt and his extra motivation in going forward with Terry's case. When Derek appeared to him in his 'dream,' it served as an awakening that he needed to move on with his life. I think this was a much better way to incorporate his character.
Ralph's therapy
I thought this was more than unnecessary in the show. It was boring and I'm glad they didn't show much of it. I can only deduce that they needed space filler. For a book that ran over 500 pages, King didn't feel the need to add this useless side story.
El Cuco's Death
When El Cuco 'dies' in the book, Holly kills him with a device known as a Happy Slapper, and stabs him in the head with it. When she does so, his head changes into all his shapeshifting faces until it crumbles inside of itself. Then a bunch of worms crawl out everywhere. Holly and Ralph make a run for it, careful that the worms don't touch them and infect them. Claude also is not in the cave with them and he and his brother never even go to the site.
The Setting
Holly never goes to New York in the book to try to trace the killings back to its original source. This might be the biggest difference. So there is no story about Maria and Rikers Island. Heath's friend Tracy is also not in the book. I can see why the show did this to add another storyline, but as Holly admitted later in the speech to the team, it was not necessary to trace the origin. So the book didn't need that part to fulfill the story.
In a smaller difference, El Cuco's hideout is in a desert wasteland in Texas in the book and not in wooded Tennessee. I'm guessing they made this change due to budget constraints, but it didn't bother me in the slightest. A cave is a cave.
Jack's character
Jack never wanted to be part of the investigative team in the book and his scar was explained in the book as cancer. He was infected with cancer just like his mother was. His mother never beat him up, but he awoke to her sleeping next to him in his bed. And he never tried to take Holly to the caves. He also never hid out with El Cuco in the caves near the end and instead of committing suicide, was shot by Ralph as he started to raise his gun at him and Holly. I like his character in both the book and the show, but I wish they would have explained the scar a bit more in the show. They kind of just showed it without explanation. I actually thought that his mother being in bed with him would have been creepier. But that's just me.
The Ending
At the end of the book, district attorney Bill Samuels (Kenneth Hayes in the show) gives his reasoning to the public as to why he's dropping the charges against Terry Maitland and announces that he's not running for office. In the show he briefly tells Glory, (whose name is Marcy in the book.) It also doesn't have that weird scene with Holly after the credits. There's more of an unsure dialogue with Holly and Ralph on if the thing is dead or not. I was more satisfied with the tame ending as seen in the book, as trying to put the past behind them. The show erred on the dramatic, which is fine. But it felt forced and unnatural.
Part of the Investigation
Ralph discovers the hooded figure in the TV footage during the killing, but he is not seen on other media outlet footage. This is a first step in knowing that there might be something off about him. He also is more quick to accept Holly's beliefs than he is in the show. Holly gave more background to her work before coming to the case, namely talking about her time with Brady Hartsfield and Bill Hodges. I would have liked if they went into this more, as it would have peaked interest in her time with other such figures.
The discovering of El Cuco
Holly discovers the tale of El Cuco from a strange woman in the prison in Rikers Prison in the show, whereas she finds a cult Mexican film about the figure that she shows to the investigative team in the book that eerily connects the crime to the movie. For the sake of time, I think the show made the right choice in this matter, but if you read the book, King did a pretty cool job of syncing the legend in there.
El Cuco Attempted Kidnapping
El Cuco never tried to kidnap the Tennessee boy from the Cave Festival in the book. This just added more drama for TV as it told the cast what we already basically knew: that he was there. It wasn't really necessary, but it made for good TV. Also, in the show, the Bolton mother is still alive and she is the one that tells of the mine collapse. They also are more hospitable to the cops than they are in the show.
Those are the main differences. There are other subtle differences, but I think overall the show did a masterful job in its own right. I still hold that the book is better and encourage viewers to watch it even if they already watched the show. You won't be disappointed.