First I want to say that I'm a HUGE fan of the books and I think Rick Riordan rocks. That being said, movies are usually different from the books for various reasons - time constraints or to add more drama. Sometimes it's for the better or it works and sometimes it just doesn't.
I thought the movie was good, not great, but good.
Things I wish had made it into the movie:
- finding out about his father - while at Camp Half Blood
- Ares
- more time with the gods
- Chariot Races
Things I LOVED
- Medusa
- Grover
Nashville and the Partheon - Yes, this was extraordinarily different, but awesomely so although the real statue of Athena looks like this:

Things I didn't like
- Luke - I didn't feel he was evil enough - seemed a little cheesy to me
- Capture the flag
- Mrs. Dodds not as a Math teacher
- The Gods' height, not in human form - felt really strange to me.
Things I didn't mind
Overall I do hope they continue with Sea of Monster