AWESOME!!!!!!!!!!!!! Apollo's character development was so good. Things that made me really happy: 
 (view spoiler)[ 
 1. Percy Jackson is going to have a little sister!!! 
 2. Solangelo!! 
 3. Apollo and his children 
 4. LEO's RETURN!!! 
 5. Caleo! 
 Also I love how we are told about things that occurred back in PJO and never found out, how this group was behind Luke Castellan's rebellion and orchestrated Gaia's war. (hide spoiler)]