Alan (Keele University, UK) Wright 
Policing: An introduction to concepts and practice [PDF ebook] 

This book provides a highly readable introduction to the role and function of the police and policing, examining the issues and debates that surround this. It looks at the  »core functions » of the police, the ways in which police functions have developed, their key characteristics, and the challenges they face. From the outset questions are asked about the conceptual contestability and ambiguity of policing, and different views of police roles are addressed in turn: policing as social control, crime investigation, managing risk, policing as community justice, and as a public good.