This book is on pre-order until release date of September 22 and book delivery arrives. 
 
Shadows of the Timberlands (Moonstone Isle #2) by Ashley Adams:
 
Now in the clutches of his father, Flint must learn how to use his newfound powers to defeat the beasts created by Slate’s chaos. Luckily for Flint, he has always known a life of thieving and survival. He must now use those skills to keep himself alive as he battles evil creatures, lost souls, and his own mind.

After being threatened by the deities of Moonstone Isle, Slate, God of Death, isn’t taking any chances at losing his heir. A series of obstacles are thrown Flint’s way, each one a new challenge that drives him closer to learning who he truly is.

But not every obstacle Slate creates is in the form of a beast or monster. He sends Nova, his mortal servant, to distract Flint and become his weakness. Nova and Flint become reluctant allies, both wanting to escape their fates in the Underworld.

Flint is inspired to turn the Underworld into something better, something worth dying for. But first, he must learn how to kill a god. In order to defeat his father, Flint must find the hidden truths that will have him questioning his entire existence.

Welcome to the Underworld.
Where monsters lurk in the shadows and you can’t trust anyone.