First published back in 1993, Bullying at School by Dan Olweus though somewhat dated, is still an informative read for anyone who wants to better understand bullying and how it can be prevented. While a few school officials and at least one school safety consultant claim that bullying is not really a significant problem, researchers like Olweus have provided us with numerous peer review studies that document the problem and the need for evidence-based approaches to reduce its impact.
After many years in the field, I still recommend this classic and ground-breaking book.