The central relationship in Gabrielle Zevin’s best-selling novel “Tomorrow, and Tomorrow, and Tomorrow” is the lifelong creative partnership between Sam and Sadie, childhood friends who go on to start a video game company. The novel depicts the exhilarating highs and enraging lows of collaboration, including fights over recognition — that is, how Sam and Sadie see each other’s contributions to their work compared with how the world sees them.