I really loved all the Percy Jackson series. It was wonderful to see how all the parts connected in the end, no lose ends. I love that these books don't leave anything open to interpretation and explain the story very well. I really enjoyed all the adventure, it was great! The characters are also very easy to empathize with, I already miss Percy and Annabeth.
The one thing that left me a bit disappointed about this book in particular is that with it being the last one in the series revolving around the first great prophecy, and Percy finally having to play his very important part, I expected more conflict on him. Percy is under a lot of pressure and tension, I think it would have been more realistic, and more pleasing therefore, to see more conflict go on within him, to see him struggle a bit more to make the right decisions and therefore see some growth in his own personality, to go deeper and give more meaning to the "yealding" Hestia talks about. In short: I think we didn't see Percy really "yealding". It seems that everything was a bit too easy for him when it came to making decisions. That felt too unreal. I feel that the whole topic of yielding, maturing, being generous and really having to struggle to get there, which is what most have to go through, wasn't represented in a realistic manner. It was too simplistic.
On a final note, as much as I have found this new take on mythological stories fun and entertaining, I'm not sure I'll read the other books in The Heroes of Olympus and The Trials of Apollo series. It gets boring if you only read about the same thing. It would be great if the author wrote about other things besides mythology, and offered us new adventures to read without having anything to do with mythology.