I'm a book fan and they left out everything. They under-complicated the whole book making it cheesy and corny. For example: Luke's body was possessed by the titan who manipulated him into helping him and under control, in the end, Annabeth talked about how he broke their promise to be a family, and he killed himself to stop Kronos the titan(even then so much happened before this scene like an army and a battle in NY). Luke also had a complicated childhood and backstory. In the movie this happened: Kronos (the titan more powerful then all the gods!) ate Luke and got killed by Percy in seconds. This makes Luke seem like just a cheesy empty villain. ANd this is just ONE thing wrong with the movie