"With a name like Gohberg–Goldberg–Kaashoek, it has got to be good. But let me count the ways. If you are interested in learning the basic theories of Hilbert and Banach spaces together with the well-known operators that act on them, this book is for you. It is intended for advanced undergraduate and beginning graduate students in mathematics.... The volume is actually a second edition of *Basic Operator Theory* by Gohberg and Goldberg.... Exercises and examples have been added.... The text is well written, clear, and readable.... A student at the specified level will have no difficulty understanding the presentation."
**—SIAM Review**

"The material is presented in a very clear way, emphasizing concepts over technical generalities. Another pleasant feature of the book is the large number of examples and exercises. In summary, the authors have successfully found an interesting way from the elementary level to some of the highlights of operator theory."

**- Monatshefte für Mathematik**

This book provides an introduction to functional analysis with an emphasis on the theory of linear operators and its application to differential equations, integral equations, infinite systems of linear equations, approximation theory, and numerical analysis. As textbook designed for senior undergraduate and graduate students, it begins with the geometry of Hilbert spaces and proceeds to the theory of linear operators on these spaces including Banach spaces. Presented as a natural continuation of linear algebra, the book provides a firm foundation in operator theory which is an essential part of mathematical training for students of mathematics, engineering, and other technical sciences.