The Wolves of Ruin #1 Dire Bound (hardcover) Sable Sorensen

Meryn Cooper has always hated the Bonded, elite warriors who form mental links with the massive, vicious direwolves they ride. While they live in luxury, Meryn struggles to keep her family out of poverty. When her little sister, Saela, is kidnapped—stolen across the border by the immortal monsters her country has spent centuries fighting—Meryn’s world falls apart.

Desperate to cross the front and save her sister, Meryn enlists in the army and is thrown into the deadly Bonding Trials, where any mistake will cost her life.