This book is written for patients and members of the public who want to understand more about the approaches, methods and language used by health-services researchers. Patient and public involvement (PPI) in research is now a requirement of most major health-research programmes, and this book is designed to equip these individuals with the knowledge and skills necessary for meaningful participation. Edited by award-winning mental-health researchers, the book has been produced in partnership with mental-health-service users and carers with experience of research involvement. It includes personal reflections from these individuals alongside detailed information on quantitative, qualitative and health-economics research methods. An electronic edition of this book is freely available under a Creative Commons (CC BY-NC-ND) licence.