The Sea of Monsters by Rick Riordan

The Sea of Monsters by Rick RiordanAfter a year spent trying to prevent a catastropic war among the Greek gods, Percy Jackson finds his seventh grade school year unnervingly quiet. His biggest problem is dealing with his new friend, Tyson a six foot three, mentally challenged homeless kid who follows Percy everywhere, making it hard for Percy to have any "normal" friends. But things don't stay quiet for long. Percy soon discovers there is trouble at Camp Half Blood: The magical borders

Except when I show up for my new job to teach a little girl how to ride her horse

unwelcome and known to disappear without a trace

And no way to figure out what's happened

including the enigmatic Mirror Prince

whose defeat can only come through fire

but I have

My Fault is the first book in Mercedes Ron's Culpable trilogy

But he was everything that gripped me

Violet awakens a dreaded curse

Valeria finds refuge with the Thieves Guild

one of her brothers will die

In the beloved tradition of Howl’s Moving Castle