Root's evocative watercolor and pen-and-ink drawings in deep sea blues and greens are perfectly allied with Hopkinson's stirring tale, set off the coast of Maine in 1855, of a girl's life as a lightkeeper. Bertha Holland, known as Birdie, starts a diary when she's ten that takes readers through the year her father leaves sailing to become keeper of a lighthouse. Her brother, Nate, becomes a fisherman, but Birdie loves the look of the sea from the tower and the work of caring for the lamps, filling them with oil, and making sure they burn through the night to guide sailors to safety. When her father takes ill, she keeps the lamps working throughout a fierce storm, and finds that she has guided to harbor Nate's fishing boat. Period details and a spirited heroine with a clear voice make this book a genuine delight. Hopkinson notes that although Birdie is a fictional character, she was inspired by several real lighthouse keepers, among them Grace Darling of England and Abigail Burgess Grant of Maine. (Picture book. 5-9)