Novice and expert designers think very differently. The big challenge in engineering education is developing inexperienced designers into professionals who think like expert designers. The key to developing expertise is mentoring learners in design thinking as they work with real design challenges. The book, Design Thinking, is created to provide problem-specific mentoring within individual design teams. Team members learn by testing their knowledge, reflecting on its success, revising understanding as necessary, and performing at higher levels with the advice of an experienced mentor: the Design Thinking book.The Design Thinking book is constructed around brief mentoring sessions that occur in the context of actual work of the team. Teams gain just-in-time assistance through a focused discussion on the task at hand. Members discuss questions posed and identify actions needed to refine or complete what they are doing. Team members collectively increase their understanding of the design work they are doing, identify errors or oversights in their work, and improve upon their design.By using exercises in Design Thinking, inexperienced designers practice critical review of their design processes and intermediate design products before costly mistakes are accepted without question. These pauses to reflect also invite creative ideas for improving solutions and their value. In the end, design teams produce more valuable design products and become more valuable design professionals in their future career paths. Be smart! Develop design expertise now, and it will produce exceptional dividends in the future.