So B. It is a touching coming-of-age story from acclaimed author Sarah Weeks. The novel follows a young girl named Heidi, who embarks on a cross-country journey to uncover the truth about her parents. Her life with her mentally disabled mother is filled with mysteries, including the enigma of a peculiar word in her mother's limited vocabulary.

As Heidi travels far from home, she pieces together the puzzling history of her family. Her journey is one of discovery and self-acceptance, ultimately teaching her that sometimes, understanding comes from accepting the unknown.