I've heard some complaints from people who like the book series, but I have to say that I like the movie adaptations. In fact, I like it better than the Harry Potter movie adaptations. The Harry Potter adaptations followed the books rather closely, which only made things all the more painful for the book fans when the movies deviated from the books, in favor of weird things. (See: Harry Potter 3)
The Percy Jackson movies are much more loosely based on the book series. That's both good and bad. On the bad side, they left a lot out of the first movie, such as Mr. D, Clarisse, Thalia, the prophecy and Kronos. They had a major hurdle, in fitting all of that backstory into this movie, so things would make sense. The good news is that I think they did a magnificent job with this task.
One way they handled this was by giving Luke a villain upgrade. In the book, he shows up once, on the yacht. In the movie, he shows up three times: as the villain who poisons the tree, on the yacht, and at the end, he temporarily steals the fleece from our heroes (more on that later). Is that following the book? No. But it made things more cohesive, it fit in well with two of the subplots (Thalia's tree and Hermes), and it made the ending showdown all the more exciting because the movie was building up to it. Plus, Luke's actor does a great job; I find him more interesting in the movies than in the books.
Another way they handled the adaptation was changing Percy's motivation. In the book, Percy wants to save Grover, and that's mainly it. In the movie, Percy's main motivation is the fact that he feels inadequate. He's depressed, because he failed a lot of quests in between the two movies, and he doesn't think he has what it takes to still be a hero. It's different, and it fundamentally changes his relationships with Clarisse.
In the book, Clarisse is portayed as a second fiddle to Percy, and she wants to prove that she has what it takes to finish a quest. The situation is almost reversed in the movie. Here, Clarisse is the main hero of the camp, while Percy is more of the aging underdog whose glory days are probably behind him. That also changes the effect of the ending where Clarisse cooperates with Percy. It's more of a victory for them when they cooperate, whereas in the book, it's more like Percy having pity on Clarisse's failure.
The most obvious change--besides for the fact that our heroes are eaten by Chabydis and have to fight out of her stomach--is the part with Polyphemus. It takes place in a run-down amusement park, instead of the island from The Odyssey. He's less threatening in the movie than in the book, because they shrunk him down from 20 feet to 8 feet. Also, the heroes don't fight him directly; the confrontation with Polyphemus is more like a chase sequence.
Our heroes steal the fleece and escape the cave. They trap Polyphemus inside, by rolling the giant boulder over the entrance. Um...yeah. Apparently, two teenagers can move the boulder, but Polyphemus can't. You don't have any time to think about why this soluion could not possibly work, because our heroes almost immediately run into Luke and the bad guys.
The bad guys shoot Tyson and steal the fleece. They tie up our heroes with large ropes that have plenty of slack, so they can easily move around. To be honest, I don't think our heroes would have trouble escaping, even if Percy didn't have a magical sword. Meanwhile, Luke uses the fleece to bring Kronos back to life.
Yep, Kronos comes back to life and wreaks havoc for a while. Percy and the others fight him, while his body is reforming. Conveniently, Percy's magic sword happens to be Kronos' weakness. I'm not sure how I feel about that. The movie did have foreshadowing leading up to this plot twist, but it still came as a surprise to me. I'll probably rewatch the movie before deciding if it's a good way to defeat the large villain, or a cheap, last-minute trick.
Overall, I liked the movie just as much as the first one. Which makes sense, because it's pretty much the same thing as the first one. The two movies are cut from the same cloth; this one is not significantly better or worse than the first.
- Apparently, the "h" in "Thalia" is silent. So...I've been pronouncing it incorrectly for years.
- Mr. D was hilarious. Good job.
- Grover is kidnapped halfway through the movie, instead of at the beginning. This works for me, because Movie Grover is a lot better than Book Grover.
- On the other hand, I think Book Tyson is better than Movie Tyson. I didn't particularly care for him, and I imagine his role would have been larger if they didn't need to spend so much time catching up on other things.
- The only time I disliked Percy's acting was during the scene where Annabeth talks about Thalia's death. He reacted way too casually, for such an emotional scene.
- Absent from the movie are the hydra (which was in the first movie), the sirens, the Lastrygonians, and Circe. Rainbow the hippocampus was there, and I expect to see hilarious My Little Pony seapony jokes now.
- Clarisse's first mate, who gets a few lines, is named Riordan. I see what they did there.
- The movie has the same ending as the book, mainly because it is the perfect cliffhanger which cannot be improved upon.