The Amazing Story of Adolphus Tips by Michael Morpurgo. 

This book is framed by a modern story, but the heart of the book is the story of a girl living in Britain during World War II.  The girl, Lily, has a cat named Tips who she adores and lives in a small village with her grandfather and her mother.  Her father is off fighting in the War.  Then her village is evacuated so that the Allies can practice their training for D-Day.  When they evacuate, Lily loses Tips.  But a wonderful American soldier is there to try to help her find the cat.  The story has a great old-fashioned feel to it, combined with a spunky girl who never gives up.  It captures a fascinating moment in history in a child-friendly way. 

This would make a great read-aloud in classrooms that are studying World War II.  It is appropriate for third through sixth graders.  Recommend it to children interested in history or animal stories.