There are two fundamental questions that should be answered before buying, and even more before reading, a book. \(\bullet \) Why should one read the book?, \(\bullet \) What is the book about?
This book would not have been possible without the help of several persons. First of all we wish to thank Lakhmi Jain and Helen Desmond who managed the book proposal submission. Then we thank those who helped us to significantly improve the original manuscript: the copyeditor at Springer-Verlag and our colleagues and friends Fabien Cardinaux, Matthias Dolder, Sarah Favre, Maurizio Filippone, Giulio Giunta, Itshak Lapidot, Guillaume Lathoud, Sébastien Marcel, Daniele Mastrangelo, Franco Masulli, Alexei Podzhnoukov, Michele Sevegnani, Antonino Staiano, Guillermo Aradilla Zapata. Finally, we thank the Department of Science and Technology (Naples, Italy) and the University of Glasgow (Glasgow, United Kingdom) for letting us dedicate a significant amount of time and energy to this book.