Wendy Mass has written 31 novels. Many of her novels, including 11 Birthdays, are coming-of-age stories that incorporate a magical element. Mass aims to inspire her audience of children, preteens, and teenagers through her works, which urge readers to live authentically and to treat others with kindness. 11 Birthdays is the first of five novels in Mass’s Willow Falls series.

In 11 Birthdays, both Leo and Amanda learn about the importance of prioritizing authenticity over the good opinions of others. This message runs through many of Mass’s works; she is aware that her young audience is at a stage of life where peer pressure and bullying are particularly prevalent, and her characters’ journeys model resilience and the importance of being true to oneself. For example, in Mass’s novel Every Soul a Star, a wise character counsels another that “[t]he trick is that as long as you know who you are, and what makes you happy, it doesn’t matter how others see you.”

Mass also impresses on her readers the importance of empathy; many of her characters, both protagonists and side characters, suffer silently with feelings of sadness and loneliness or struggle with decisions or challenges that other characters are unaware of.