Just because this section is called "the Historical Books" does not mean that the other books of the Bible are not historical, nor does it mean that these books portray verified historical events. This section of the Bible (Joshua-Esther) tells the story of Israel from entering the promised land to the return from exile. Here's a brief outline of what's to come:
Joshua & Judges: Settlement in the Promised Land and God's rule. Israel's tribes are established and land allotted.
1st & 2nd Samuel: The rise of monarchy in Israel (esp. David).
1st Kings: Solomon's reign and the construction of the temple
2nd Kings: Israel splits (Israel in the North, Judah in the South). First Israel falls to Assyria (722 B.C.E.) then Judah falls to Babylon (587 B.C.E.)
1st & 2nd Chronicles: Retells the history of the monarchy (though written from a post exilic perspective.
Ezra & Nehemiah: people return from exile and rebuild Jerusalem.
Ruth: Written as a response to the exclusiveness and xenophobia of Ezra.
Esther: story of a Jewish heroine's faith while in exile
What's the book about?
Joshua was a warrior and Moses' apprentice through the wilderness. After Moses dies (Deut. 34), God commissions Joshua to be the next leader of Israel and the one who brings them into the Promised Land. This book portrays Israel's great success in claiming their inheritance and completely destroying the inhabitants of the land. The last portion of Joshua details the land distribution between the tribes.
How should I read it?
Joshua is the first of the historical books, however the details in the book (especially the complete annihilation of the Canaanites) is not historically accurate. Keep in mind, this book was finished in the 7th century B.C.E while Israel was in exile. Joshua contains epic poems, battle strategy, and legal language. I encourage you to read this book as one might relive the "Glory Days," embellishing the story to boost morale when reality is actually quite grim.
Part I: Claiming and Conquering the Promised Land (Josh. 1-12)
Israel annihilates the inhabitants of the land.
Part II: Dividing the Land Among the Tribes (Josh. 13-22)
Some tribes, like Levi, are exempt.
Part III: Repent and Renewal of the Covenant
God has been faithful in his promise to bring them to the land, now Israel must be faithfully devoted to God and God alone.
Holy War is a theological question with which we must wrestle. How is it that God, Creator of all things (including the Canaanites), encourage and demand annihilation of a people? I will offer just a few scholarly responses here:
It didn't actually happen. "Archaeological evidence demonstrates--and the book of Joshua itself acknowledges--that the 'conquest' of Canaan did not result in the annihilation of the native population." (Kathryn Schifferdecker)*
It isn't God's intention. "God works with what's available, including the institutions of society. Institutions in that ancient context include certain ways of waging war....Violence will be associated with God's work in the world because, to a greater or lesser degree, violence characterizes the people and institutions in and through which that work is done." (Terence Fretheim)**
How might you explain the horrible violence in Joshua? Throughout history? Today? Where's is God in the midst of it?
If you are asking these questions, or similar questions, congratulations! You're a theologian!
Whether they are going into battle against five kings, sieging Jericho or settling into their designated territory, God expects Israel to remain Obedience. Perhaps it was easier to be obedient when they had no other option in the wilderness. Whatever the reason, Joshua urges the people of Israel to remain obedient to God's law so they may live. Obedience leads to life and prosperity. Disobedience leads to death and destruction.
* Schifferdecker, Kathryn . “Joshua.” Enter the Bible, http://www.enterthebible.org/oldtestament.aspx?rid=26, Accessed 14, March 2017.
**Fretheim, Terence E. About the Bible: Short Answers to Big Questions. Minneapolis: Augsburg Books, 2009, p.135.