This is just bad, just bad. Very poorly written and doesn't explain things that needed to be explained. If your looking for a movie based of the book, this is only Artemis fowl in name only. Artemis is said to be a criminal genius, but we only see he is a genius by recognizing forgery once, and being told he a genius, that is it. Nothing else, he is more of a lame action movie hero, not a genius. Mulch wasn't bad, had some pretty funny lines. I would recommend if you love watching stupid movies though. (Spoilers from here on out, going from mild to severe spoilers in order).
(mild) Mulch is narrating the entire story to the human police.... Why would you do that? How do you tell the parts of the film that you weren't there for? With you on the loose, how have the fairies not been discovered yet?
(mild) A troll is throwing around adults, threatening to kill them, and Holy heals the kid that was thrown into the air, and is a little dazed ,yea, thanks Holy.
(severe) Why in the heck does Artemis kidnap Holy? In the book he has a perfectly good explanation, but in the movie, he wants their help? He kidnaps Holy, so they will send mulch to steal the super weapon in their own home? Could he not find the super weapon in his home behind a painting? If he wanted their help, it wasn't a good idea to kidnap one of their officers, and basically wage war with them.
(severe) We are shown that a time bomb can freeze everything in an area, except the fairies, so why did they freeze THE ENTIRE WORLD (I think? At least that was what was implied) and not fowl manner? In the books, the fairies can't go into a house without permission, but I don't think that is explained in the movie.
(severe) We are told that the time bomb's explosion will be dangerous, but when it explodes, everyone in the area is completely fine WITH NO EXPLANATION.
There is so much more, but these are the ones that bothered me the most (and the ones I want to vent about), all in all, made the lightning thief look like a cinematic master piece.