The War That Saved My Life by Kimberly Brubaker Bradley

Ada is an abused 11 year old girl living in London just before the outbreak of World War II.  Her hateful mother keeps her imprisoned in the apartment, falsely telling neighbors that Ada is trouble and unfit for social interaction.  Ada's younger brother Jamie freely roams the neighborhood knowing that Ada's only problem is that she has a "bad" foot..  Ada manages to teach herself to walk though terribly painful.  When London children are being evacuated to the country to avoid anticipated German bombs, the plan is to leave Ada behind.  Instead she secretly joins Jamie on the train load of evacuated children.  As children are selected by reluctant villagers Ada and Jamie manage to stay together and remain unchosen.  The woman in charge forces them on the recluse Susan Smith.  Though at first reluctant to care for Ada and Jamie, Susan is clearly a kind person and is greatly troubled by Ada's constant flinching every time Ada makes a mistake.  Ada is slowly transformed by the kindness she receives.  Her love of horses helps her to meet new people and experience new confidence. Though understandably prickly, readers can't help to warm to Ada, a clever, loving, girl despite the damage her mother has inflicted upon her.  You'll want to know what happens to Ada and Jamie as the war develops and begins to reach not only London but the countryside.