https://www.osa-opn.org/home/book_reviews/2020/0220/the_new_international_system_of_units_(si)_quantum/

Metrology is the science of measurement, and the International System of Units (SI) is the standard for those measurements in fields such as science, engineering and economics. This book contains a complete review of the revised SI, which came into force on 20 May 2019. While this book is based on a previous book by the same authors, “Quantum Metrology: Foundations of Units and Measurements,” it is reorganized and revised with new SI definitions and the differences between the previous and the present SI. The book explains and illustrates the physics and technology behind the definitions and their impact on measurements, emphasizing the decisive role quantum metrology has played in the revision. The individual chapters are updated through the inclusion of the latest results and progress. This book addresses advanced students, researchers, scientists, practitioners and professionals in the field of modern metrology as well as a general readership interested in the foundations of the new SI definition.