“This is a truly stunning collection of material which is certainly most welcome.” (R. Steinbauer, Monatshefte für Mathematik, Vol. 192 (1), 2020)<br />“This book is full of interesting problems. This is a useful collection of problems (with complete solutions) in pure and applied nonlinear functional analysis. … The volume is also addressed to graduate students and to researchers in pure and applied analysis. … this volume is an excellent gateway to the culture of problem solving. It is challenging and rewarding. The book shines a new light on mathematics and engages readers with its wonderful insights and problems.” (Vicenţiu D. Rădulescu, zbMATH, 1351.00006, 2017)<p></p>