Sefer Shoftim, while it tends to revolve textually around a series of inspired regional leaders, really traces the story of Israel's tragic lethargy.  The minority of tribes are involved in the continued conquest of Canaan but the vast majority of tribes are not. The Torah commanded the nation to uproot the Canaanite Nation from their midst and sure enough, it was not possible for the people to suffer an unrepentant Canaanite population in their midst while remaining aloof from their cultural and moral values.

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion