This book, "Relentless," by Tim S. Grover, explores the concept of achieving peak performance through intense mental and physical conditioning. Grover categorizes competitors into Coolers, Closers, and Cleaners, with the latter representing the ultimate, unstoppable mindset. Drawing on his extensive experience training elite athletes like Michael Jordan, Kobe Bryant, and Dwyane Wade, the author reveals the unconventional and often harsh methods required to cultivate a "Cleaner" mentality. He emphasizes the importance of embracing a "dark side" of controlled anger and innate instinct, rather than relying on conventional motivational techniques or focusing solely on physical talent.Ultimately, the text argues that true success stems from an unyielding commitment to self-improvement, a refusal to accept failure, and a willingness to do whatever it takes to achieve desired results, irrespective of external validation.The book also mentions a supplementary program, "Jump Attack," which focuses on the physical application of these mental principles.