Awful. They completely ruined everything I loved about the book.
Even if we're not comparing it to the book, the plot was confusing, typical, and not interesting with washed out, typical characters and a washed out, typical, cheesy script.
The worst thing was all the little, unnecessary changes they made. It felt like a punch in the gut to anyone who read and loved the books.
For example: Butler. Why do they have to give him awful, weirdly blue contacts? Why do they have to bleach his hair? Why do they have to make him the stereotypical tough-guy-who's-actually-a-softie-but-can't-show-it, but with no personality? Why is Juliet 12? Why can't she be his sister like in the books? And, in heaven's name, why do they have to use his name?! To anyone who's read the books, we know what a big deal Butler's name is. It's his entire life that he has to keep secret that he only reveals to Artemis in the books when he thinks he's dying. The fact they dropped with something as lame as "but you can call him Dom" is disgraceful to his character. Another point. They introduce him as some martial arts genius and good at so many different styles to martial arts/fighting, and they deliver none of that. While we're on the not-delivering train, let's talk about Artemis.
Again, they started telling us how Artemis is a genius, and yet he discovers/plans NOTHING. He isn't smart. All he does is get upset when his dad is called a criminal, scream for his dad a lot, and then suddenly call himself a criminal mastermind...just no. The best scene in the movie was the scene when he's talking with the therapist...because that's a scene from the book! It doesn't seem like it should be so hard to make a decent adaptation of a book. It felt like the writers were seeing how mad they could make fans in the first two minutes of the movie: have Artemis surf, make him active, make him wear jeans and a beanie, make him dependent on his dad, etc. etc.
Now for Holly. One of the main motivators for Holly was that she was the first female lep.recon officer. They ruin that right off the bat by making Root a woman. I'm all for being inclusive and diverse, but when Holly being the first female is such an important plot point, it's not something to mess with. Then they make it even worse by making Holly some nube who's never been in a pod before, she's not even a captain. Instead, they give her the typical dead father who's name needs to be cleared so she and Artemis have something to bond over. The washed out relationship between Holly and Artemis is what happens when you try to smash 8 books of character development and relationship building into 1 hour and 15 minutes.
There were 8 books of incredible, interesting plots they could have gone with. In fact, the first book doesn't end on a cliff-hanger. It could have been a just fine story all on it's own, but they feel the need to change everything about it. They took a loved and unique story and washed it out. Just like the characters who all felt like washed-out versions of their original characters. In fact, thinking about comparing the movie characters to the book characters is so hard to do, it's hurting my brain. I could go on forever and ever, but I've ranted long enough. Now excuse me as I go cleanse my pallet by reading the books.