Artemis Fowl is not an adaptation. It is a movie that borrows locations, plot elements and character names from the best selling series, and proceeds to create a new movie original McGuffin centered plot, that is given far too little time to properly unfold with the film cramming in iconic moments from the book that fall flat in the film as they no longer make sense given the different direction of the plot, not to mention the drastic changes made to character motivations and their overall characterization. Also this film HEAVILY replies upon a narrator and exposition to tell you how cool and interesting people and things are, but never really shows it.
However I will not dwell on this, and turn instead to the big changes that left the story weakened. Artemis is no longer the antagonist or a criminal mastermind, who happens to be a child also, but instead he is a socially awkward and intelligent child who wants dad back, and comes up with a convoluted plan that relies on luck at the end of the day to get his dad back by magic. our new antagonist(s) are weak at best with little to no direct confrontation, being at best observers and irritants in a conflict started by Artemis for a plan that relies on luck.