Twenty years ago, Abigail Sorenson's brother Robert went missing one day before her sixteenth birthday, never to be seen again. That same year, she began receiving scattered chapters in the mail of a self-help manual, the Guidebook, whose anonymous author promised to make her life soar to heights beyond her wildest dreams. The Guidebook's missives have remained a constant in Abi's life -- a befuddling yet oddly comforting voice through her family's...

Fourteen-year-old Madeleine of Cambridge, England, struggling to cope with poverty and her mother's illness, and fifteen-year-old Elliot of the Kingdom of Cello in a parallel world where colors are villainous and his father is missing, begin exchanging notes through a crack between their worlds and find they can be of great help to each other.