Judith Viorst was born and brought up in New Jersey and now lives in Washington, DC. Her books include the beloved Alexander and the Terrible, Horrible, No Good, Very Bad Day, and its many companion books; adult fiction and nonfiction including the New York Times bestseller, Necessary Losses; poetry for children and adults, and four musicals.

Her most recent book of poetry for children, What Are You Glad About? What Are You Mad About? was published in 2016. Lulu Is Getting a Sister is the fourth book in the Lulu series.

Robin Preiss Glasser, who habitually sports glasses and jeans, discovered her "inner Nancy" while illustrating this book. "Wearing lace-trimmed socks helps me draw better," she says. She has illustrated many books and lives in Southern California with her family and tiara collection.