This book is basically one long final battle, and as such, it's a fitting climax to the series.
[Unmarked spoilers ahead.]
It starts off with Opal Koboi (again) enacting her Very Definitely Real Final Master Plan, involving having herself killed (the "herself" in question being a past version of herself who tagged along with Artemis when he returned from the past in The Time Paradox) and also stuffed down a nuclear reactor so when she explodes from this actual time paradox it doesn't destroy anything important. Except because this is Opal Koboi's Very Definitely Real Final Master Plan™, it actually turns her into a ridiculously powerful magic person.
The usual gang (that being "Artemis, Holly, Butler, and eventually Mulch Diggums, possibly with Foaly support") assembles to stop her from opening some magic gates and unleashing ancient obliterate-ALL-the-humans! magic. Artemis's brothers (of The Fowl Twins fame) also feature in this one, though mostly because they got possessed by some ancient ghosts Opal also unleashed.
This is pretty much the best way the Artemis Fowl series could have ended. It completes Artemis's character arc, it defeats recurring villain Opal Koboi for good this time, it (briefly) brings back stuff from all the way back in book 1... my only quibbles, really, are the somewhat ham-fisted "this is how the world went on spinning after Opal Koboi blew up half the tech in it" epilogue parts. (To be clear, it's not the fact that they were in there, we needed to know how it worked. It's how the author chose to do those that irked me.)
I think this post would also be a good place to talk about the overall arc the series took in quality. It started off quite strong with the original Artemis Fowl, dipping very slowly down from Arctic Incident through Eternity Code to Opal Deception before hitting another peak with Lost Colony. Then it dove off a cliff into Time Paradox, crawled out of the ground with Atlantis Complex, and came back strong for this one. Did that make sense? No? I can do a ranking later if anyone wants.
Were this a videogame, I'd rate it: T. It's good to know this series didn't pull a Mr. Terupt and steadily increase in content level over the course of it.
4 stars.
(Endnote: I'm not actually sure who the titular Last Guardian is. Maybe the ghost of the original guy who set up the ancient obliterate-ALL-the-humans! magic in the first place?)







