The book of Judges shows how corrupt God's leaders and people can become but offers hope for the future.
After the death of Joshua, the people of Israel begin a downward spiral. Israel begins to adopt the corrupt practices of the Canaanites they failed to drive out of the land. This leads to a repeated cycle of sin, oppression, repentance, deliverance, and peace, which only eventually leads back into sin.
The book of Judges highlights six judges during this time and shows their increasing corruption. These judges start off fairly well (Othniel, Ehud, Deborah) but become increasingly worse (Gideon, Jephthah, Samson). The book ends with two very disturbing stories that show how incredibly lawless the people have become. The central verse that summarizes this says, "In those days Israel had no king, and everyone did what was right in their own eyes."