Aftershock by Katherine Armstrong Walters is Book 2 in the Arydian Chronicles.
WARNING MAY CONTAIN SPOILERS
At the end of book 1 Aqua, we are left with the California coastline in ruins due to an underwater earthquake and tsunami.
Marin and the Arydians have had to abandon their secret underwater home and are now on the run from Mr. Haan and Leviathan, the secret organization bent on taking control of the World.
Jayson is torn between staying with Marin the girl he loves and going home to search for his mother. He ultimately chooses to leave, unsure if he will ever be able to find Marin again. Before leaving he steals something from the Arydians that may lead to the destruction of Marin and all her people.
Mr. Haan is obsessed with his search for Marin and will destroy anyone who gets in his way. He has also been hard at work and created a weapon that could destroy the world as Marin knows it.
Walters did a fantastic job. Often times the second book in a trilogy can be slow, drawn out and a bit disappointing. But Aftershock is full of surprises. The momentum builds with each chapter. I thoroughly enjoy book 2 and couldn't put it down. I can't wait to see how Katherine wraps it all up in the final novel. My only complaint is that now I have to wait for book 3!