The book "Ultra-Low Energy Domain-Specific Instruction-Set Processors" offers a comprehensive analysis of the challenges and solutions in the field of energy-efficient processor architectures for mobile devices. Given the increasing demands for computing power and functionality in modern electronic devices, it is crucial to develop processors that are both powerful and energy-efficient. The authors, including renowned experts in the field, highlight the necessity of a holistic approach to the design of embedded systems. They discuss how the optimization of individual components within a complex system must be carried out to achieve a balanced relationship between flexibility, energy consumption, and performance. The book is aimed at professionals and students who wish to gain a deeper understanding of the development of specialized processors in today's technology-driven world.