The book "Least-Squares Finite Element Methods" offers a comprehensive introduction to finite element methods, which have played a significant role in the numerical solution of partial differential equations since the 1950s. Originally developed for structural analysis, these methods have proven to be extremely versatile and are now applied in various fields of engineering and science, including fluid mechanics, heat transfer, and electromagnetism. The authors Pavel B. Bochev and Max D. Gunzburger illuminate the theoretical foundations and mathematical analysis of these methods, which are characterized by their high theoretical maturity. The book is aimed at professionals and students seeking a deeper understanding of least-squares finite element methods and exploring their application in various contexts.