A look at David Aaker's 17th book. The only way to grow (with rare exceptions) is with “must haves” defining game-changing subcategories with a new or markedly superior customer experiences or brand relationship, an exemplar brand that positions the subcategory, and barriers to competitors. Subcategory-driven growth has exploded in the digital era because of technology advances and the fast, inexpensive market access made possible by e-commerce and digital communication.