The Complete Peanuts 1959-1960, Paperback

As the first decade of Peanuts closes, Charlie Brown's sister Sally makes her appearance -- first as an (off-panel) brand new baby for Charlie to gush over, then as a toddler and eventually a real, talking, thinking cast member. (By the end of this volume, she'll already start developing her crush on Linus.) All this, and one of the most famous Peanuts strips ever: "Happiness is a warm puppy."