Thorn Ogres of Hagwood by Robin Jarvis

Dark forces are brewing in Hagwood

The werlings of Hagwood live peacefully in the trees of the forest--overlooked and unbothered while they leisurely perfect the art of wergling (shape-changing). But unlike his fellow werlings, the bumbling Gamaliel Tumpin can't manage to wergle into even the simplest of forms--a mouse--like his peers. He's tormented by his sister, Kernella, and teased by his classmates. And he envies star student Finnen Lufkin, who can transform into almost any creature.

 

But wergling will soon be the least of Gamaliel's troubles. The evil elf queen Rhiannon, the High Lady of the Hollow Hill, is desperately seeking a precious possession that was stolen long ago. Her evil knows no bounds, and with her army of monstrous thorn ogres, she will not stop until it's found. The werlings' peaceful existence is threatened by death and danger--and clumsy, awkward Gamaliel will need to call on the strength within him to fight for his family and his home.