'One of its strengths is that it is a genuine textbook rather than a reference text. It is highly readable and pedagogical, giving a good level of detail in proofs, but staying concise and keeping its story clear rather than being encyclopedic. Another strength of the textbook is that it is well motivated by applications of functional analysis to other areas of mathematics, with a special emphasis on partial differential equations and quantum mechanics throughout the book.' Pierre Portal, zbMATH Open

'Everything is beautifully and clearly expressed. In short, highly recommended!' Klaas Landsman, Nieuw Archief voor Wiskunde

'… intended for students who have had, at a minimum, some prior exposure to real analysis and measure theory. It is a lengthy book, weighing in at more than 700 pages, and covers a lot of interesting material, including some topics that are, to the best of my knowledge, not easily found elsewhere in the textbook literature … the author keeps the student in mind throughout: he writes concisely but clearly, and generally includes (with relatively rare exceptions) full details of proofs. Examples are plentiful, and so is motivational discussion. Each chapter ends with a generous selection of exercises … An instructor who doesn't adopt this book as a course text might wish to keep it close at hand for interesting topics in which to spice up his or her lectures.' Mark Hunacek, The Mathematical Gazette