P.A.J Waddington & Martin Wright 
What is Policing? [PDF ebook] 

This text provides an accessible, up-to-date and thought-provoking introduction to policing for all those undertaking degrees and foundation degrees. It aims not only to inform students and prepare them for their course, but also to expose them to some of the challenges they will face as they begin their studies and/or policing careers. This book is the essential foundation for the Policing Matters series, explaining what policing is, what the police do, the context for policing and what are the main issues it faces and challenges it poses.