These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Artemis Fowl
Alternative Character Interpretation: The first book deliberately aims for this by making sure that every time Artemis does the right thing, he can explain it away as Pragmatic Villainy. The psychiatrist who narrates the book argues that Artemis is a sociopath (though admittedly not a standard case by any sense of the imagination), and warns of the tendency to view him as more noble than he really is. Later books make him more of a hero, though.
Him becoming a hero is explicitly stated to be character development. In the Eternity Code, just before the mind wipe, he says that he might become the monster seen at the start of the series. The next book reveals that he was right.
Anvilicious: Book 6: Go green, and you'll save the krakens, stop poisoning fairies with Spelltrophy, and keep the world from dying. Plus, Artemis Sr. puts emission filters on every vehicle they own, including the jet and helicopter. Though the series has dropped environmental anvils all over the place since its beginning.
Ass Pull: Eoin loves this trope or owes it money. Technology of the series doesn't appear to have any consistency: numerous vital plot points happened just because fairy technology happens to be capable to do something we weren't informed of or has a limitation never brought up before.
One short story in the companion book is set in the period between the first and the second book, aka when Artemis was still a egoistic criminal mastermind and Mulch was believed to be dead by the LEP. Holly goes to stop Mulch in his tracks, but she isn't supposed to know Mulch is even alive... Well, let's make him wear a mask! Voice? Did we mention all the dwarves' voices are exactly the same and even the dwarves themselves can't tell one from another? Because now they are.
Author Tract: Humans suck! Humans suck! Humans suck! We've just described the driving thrust of most books in the series.
Broken Base: When the film adaptation of the series was announced, fans were divided on the possible casting on Holly's actress, particularly on her skin color. It doesn't help that Colfer wants Saoirse Ronan to play Holly which adds more fuel to the fire.
Complete Monster: Debuting in Book 2, Opal Koboi is a sociopathic pixie. When she got her position at the head of her company, she drove the previous owner, her own father, to insanity. Along with Briar Cudgeon, she organized the Goblin rebellion, taking advantage of the violent nature of the Goblins and planning to betray them to take over. When Holly and Artemis beat her, she plotted her revenge, and unleashed a complex gambit in Book 4. She escaped from prison using a clone duplicate (cloning is considered an unforgivable act to faeries, as one creates new life which dies easily and cannot think for itself) had Julius Root killed, framing Holly, and then she attacked and Mind Raped a very prominent humanitarian, and had him send a probe down into the earth, to reveal the Faerie people. Doing so she expected to cause a war between the two races. In the sixth book, it is revealed that she had been experimenting on critically endangered animals to make herself more powerful. In the eighth and Final Book, her past self-came to break her out of prison, and Present!Opal hypnotizes two other pixies, and has them hold her past self, and murder her, while she pleads for her to stop. Having killed her past self, any and all things she has made or influenced in her tech-corp. explode. Communications go down, cars explode, cell-phones and various guns explode, and even the humans have their planes go down in mid air, and global communications stop. She then manipulates a number of Faerie ghosts who have been trapped on earth and want to be released. She has unleashed chaos on a global scale, and wishes to kill off all the Humans and take power.
Copy Cat Sue: Minerva is bashed for this. She's not too bad a character and Artemis beats her almost easily but she was too similar to the eponymous character and the author was trying to ship the two a little too much.
For what it's worth, that book is a Dolled-Up Installment. Colfer realized that his new protagonist was a bit like Artemis and just decided to throw him in, demoting Minerva to a secondary character.
Idiot Plot: The entire berserker threat would never have occurred if they had simply shot the future Opal BEFORE she became all powerful.
It is admittedly implied to be a result of fairy society being based off of Actual Pacifism, so that they are neither legally allowed nor morally inclined to shoot a prisoner. Although that explanation doesn't make much sense given Artemis and Butler were also present and seemingly neither of them even thought of it.
They were present in the control room in Haven, not the cell block in Atlantis. They could suggest it but not do it. They probably did think of it but knew there was no point saying anything.
Inferred Holocaust: In The Last Guardian, a good chunk of technology, both human and fairy, ceases to function. This leads to chaos on both ends, but the humans bare the brunt of it as cities darken, people loot, medical equipment is useless, and airplanes fall from the sky. Nobody particularly dwells on this.
Mary Sue: Mulch Diggums. He has new powers as the plot demands, can get out of any situation (except as the plot demands), and always shows up in the nick of time to save the protagonists.
The Untwist: In the first chapter of The Last Guardian, Dr Argon ominously wonders if it is really possible that Artemis has been cured of the Atlantis Complex in record time. He has, and the only thing we hear of the Complex for the rest of the book are a few fleeting mentions.
Though it does seem to have badly damaged his self-confidance.
Values Resonance: Despite being said in his time as a mob boss, Artemis Fowl Sr's line about buying gold as a reliable investment and keeping it safe seems far more resonant in modern times.