A Skinful of Shadows by Hardinge, Frances

A Skinful of Shadows is a dark YA historical fantasy set in the early part of the English Civil War. Makepeace is an illegitimate daughter of the aristocratic Fellmotte family, and as such, she shares their unique hereditary gift: the capacity to be possessed by ghosts. Reluctant to accept her appointed destiny as vessel for a coterie of her ancestors, she escapes. As she flees the pursuing Fellmottes across war-torn England, she accumulates a motley crew of her own allies, including outcasts, misfits, criminals, and one extremely angry dead bear.