How I Became A Big Sister" is a children's book that explains adoption to young children. It is a simple story of how a little girl who doesn't have any siblings all suddenly becomes a big sister to an adopted child. The story is told from the point of view of the toddler, and touches on many of the concerns and fears that a child might be experiencing when their family decides to adopt. This book is a must read for anyone who is considering adoption of another child when they already have young children.