The plot was completely oversimplified. All sorts of major characters were removed and the motives blurred and misleading. The ending was modified to the point where the villain was absolutely obvious as soon as the character appeared on the screen on my first watching. My first time through, I had to wonder what the attraction to the series was, and though I would never judge a book by it's movie, the cliche script did not encourage me to pick up the series any sooner. Now that I've read the book, I find myself wondering how the movie industry can plan on doing a sequel when so much was cut from the first film.
That being said, there were some great things about seeing it on screen. I thought the casting was excellent. I love Kevin McKidd and Pierce Brosnan in just about anything and Uma Thurman is an amazing Medusa. However the movie writers took the whole story and moved it from middle school into high school, which is how I envision Percy when I read it, but I have to wonder if that's because I saw the movie first or because of how it's written? One of the things that bothers me with that though is it moves Annabeth's and Percy's relationship towards romantic, and, though that may be where Mr. Riordan is headed with them, I am enjoying seeing their prejudiced rivalry turn into friendship in the books, but that's what comes of aging the characters.
I liked the added scene between the gods at the beginning. It gives a little necessary plot exposition, though it does intimate a closer amount of familial relations between the gods and their children than is portrayed in the book. Although in the book we only see things form Percy's point of view, so that's an advantage of a movie, I guess.
All the while I was re-watching the film, I was wondering what the author's thoughts were on it. Apparently prior to it's release, he didn't plan on seeing the film because he didn't want it to skew his view of his characters. I have to wonder if it had been a blockbuster hit, if he could have stuck to that. What bothered me most about the plot changes were the sneaking off on the quest instead of having it assigned -it changes the tone of the movie- and the grand omission of the conspiracy part of the plot. All in all, I'm not sorry to have watched the movie (twice), even though it doesn't quite do the book justice.
Final Take: 3/5