According to the book, this movie is really inaccurate, silly and very strange. In the book, Percy didn't fight Kronos and Kronos wouldn't die easily. He even didn't met Percy until the forth book!
Princess Andromeda (Luke's ship) was supposed to be bigger and fancier and Luke wasn't fall in Polyphemus lair. Then Percy's age in the prophecy was 16, not 20 like the movie. Annabeth's dying scene was too silly and unnecessary. She supposed to fight together with Percy, not only ran away and screamed!
Sorry to say, but this movie is a
very disappointing adaptation :(