"It's Not Summer Without You" is a young adult novel by Jenny Han, published in 2010. It is the second book in the "Summer" series, following the story of Belly, Conrad, and Jeremiah as they navigate the ups and downs of their summer at the beach house. The novel explores themes of love, loss, friendship, and self-discovery as the characters confront their past and present feelings towards each other. Overall, it's a heartwarming and poignant coming-of-age story perfect for summertime reading.