This monograph brings together a collection of results on the non-vanishing of- functions.Thepresentation, thoughbasedlargelyontheoriginalpapers, issuitable forindependentstudy.Anumberofexerciseshavealsobeenprovidedtoaidinthis endeavour. The exercises are of varying di?culty and those which require more e?ort have been marked with an asterisk. The authors would like to thank the Institut d'Estudis Catalans for their encouragementof thiswork throughtheFerranSunyeriBalaguerPrize.Wewould...