This movie is so far removed from the books that it is not fair to compare the two, but even then the movie on its own probably had potential to work but instead possibly rivals the live action Avatar the Last Airbender in terms of failing to capture what is loved by so many people. I'm going to attempt to write a review about the movie itself and not how it compares to the books. Keep in mind that there may be some spoilers.
I think the producers worried that their target audience (young children) wouldn't be capable of understanding something more complex, so they made sure it was as basic as possible. The movie consists of incredibly short sentences, even shorter exchanges, and the shortest possible character development. The narrator probably has the most lines out of everyone. The writers made a fatal mistake of telling you everything that's happening rather than showing you, and it's a good thing too. If they didn't tell me that Artemis Fowl III was a criminal mastermind, I certainly wouldn't have known it. I watched the boy the entire time, and I'm not sure he did anything on his own other than furiously type at a computer keyboard and fire a neutrino(?) at some fairies.
The movie itself feels like one of those commercials that splices together moments from an entire season of shows together to give you a glimpse of what the characters and plot look like. There wasn't really enough time in any scene to develop relationships. One moment, characters are bitter enemies. And then five minutes later, they're the best of friends. Again, I think the writers were worried that children would have trouble sitting through a longer movie, so they squished as much as possible in and left room open for a sequel. However, I think they would have been better off cutting their plot ideas in half and giving each main character significantly more screen time.
The worldbuilding is incredibly difficult to follow and inconsistent, even if you've read the books. It's like the movie wants you to draw from knowledge in the books to follow things like the rules fairies have to follow in human households but just glances over them. They're seemingly important, but you could very easily miss. Very little is actually explained. I honestly couldn't tell you exactly what the villain wants or why. Just that they want it or else. The resolution is a very desperate deus ex machina which makes for a satisfying happy ending that needs absolutely no explanation. But again, I have no idea how we even got to this point.
I enjoyed some of the casting choices. Lara McDonnell playing Holly Short was cute, and with a better script, I think she would have made us proud. Josh Gad did his best to capture Mulch, and aside from the unexplained "giant dwarf" fiasco, the portrayal of him as a greasy, disgusting, thieving weirdo was nice. The unhinging of his jaw was just as terrifying as I had imagined it would be. I liked the design of Haven City as well as the LEP uniforms.
It's a little saddening to think that children's books like Harry Potter and Narnia can be brought to life in such a magical way. Are the adaptations 100% faithful to the books? No. But they keep the spirit of them. Will your children enjoy this movie? Maybe. It's colorful, clean, and simple with a few witty one-liners. But I'd recommend the books any day (or the graphic novel for those kids who don't necessarily like to read).