Book-to-Movie Law states that once you have read the book, you are bound to go see the movie based on said book, and therefor compare to two.
Oh man, the movie was terrible. Terrible for me perhaps, as I am not specifically the target audience. I can see where younger boys might like it a lot more. I was surprised by how different it was from the book. The Lightning Thief read like it was made for the big screen, but the actually movie changed around a lot of smaller details to make it feel almost like it's own entity. The main points of action were still the same, sure. But there were a lot of minor details that were changed for the movie, perhaps unnecessarily. Some were simple character changes, some chronological, others were teeny references in plot. I didn't think these changes worked to make the movie version more palatable for movie-going audiences, but maybe they did. The special effects were a little cheesy at times, too, though it was very cool to see some of those mythical creatures comes to life. Anyone know if they are working on making the second book?
Bottom line: While the movie was fun, I think boy readers would enjoy reading the book and imagining it in their own head first.