The Bone Garden — Meg Hendry

Rien has always looked up to his older brother, Arwel. When Arwel joins a group known as the Oath, with plans that endanger the whole country of Virida, Rien is determined to stop those plans and get his brother back. He believes Arwel can still come back from the path he's chosen. Rien must accept a fate he's terrified of if he's to have any chance of stopping the Oath. He must become apprentice to a necromancer, and he must become the Speaker of the Dead. The Bone Garden is a novella.