A completely satisfying end!
Kronos finally attacks, percy takes a dip in the river styx and acquires the curse of achilles, he groups all the campers and protects the city against kronos.
Nico joins the fight, Annabeth manages to awaken Luke at the very end and he sacrifices himself, they defeat kronos, everybody recieves honor and awards. Poseidon is extremely proud of his son and it's heartwarming (they hug for the first time ever). 
Percy demands that all half-bloods are claimed by their parents, and that more cabins are built in the camp, including hades!!!!! my fav!!
Percy and annabeth finally kiss for real, in front of everyone, they're official.
Rachel becomes Oracle. 

Only thing I hated was how Selena was the spy and everyone forgave her. i dont care that she sacrificed herself. 

Anyway. super heartwarming ending, with the campfire and racing over the hills and the camp repopulating.