The Book of Joshua marks the fulfillment of the Exodus of the Israelites from Egypt, for God fulfills his promises to Joshua, the successor to Moses, by leading them to the Promised Land. With God's help, the tribes of Israel united as a single people conquer the land of Canaan, and God assigned each tribe their separate territories.
The structure of the Book of Joshua is straightforward: the first twelve chapters relate the crossing of the Jordan, the fall of Jericho, and the conquest of the land; and chapters 13-22 comprise the Allocation of the lands. In the Epilogue (chapters 23-24), Joshua reminds the Israelites all the gifts the Lord has given them, and then remarks in 24:15: "But as for me and my household, we will serve the LORD.” He then renews the Covenant between God and his people before his death, in which, like Moses, he is called a "servant of the Lord."
The Book of Joshua is dramatic and contains three well-known miracle-filled episodes with Joshua, under the auspices of the Lord, leading the Israelites: the crossing of the Jordan River (3:1-4:24); the circling of the city walls with the Ark of the Covenant in the battle of Jericho (6:1-27); and the day the sun stood still in the conquest of southern Canaan (10:12-14).
An important theme of the Book is repeated in the beginning: "As I was with Moses, I will be with you" (1:5 and 3:7). God assures Joshua He will be with him (1:9). This theme is developed as Joshua is compared to Moses (4:14), and repeats many of his actions throughout the Book. Joshua is a leader without hesitation, and is portrayed as the ideal leader of Israel, a prototype for the future Kings of Israel, one who keeps the teaching of Moses in its entirety (1:7-8, 11:15). Joshua formalizes the Deuteronomic Covenant on Mount Ebai (8:30-35) following the conquest of Jericho, and renews the Covenant in the Epilogue. The Epilogue is key to understanding the history of Israel. God fulfilled his promises to the people; Joshua warned the Israelites to remain obedient to the Covenant if they wished to retain the blessing of the land.
The Book of Joshua in its entirety is a prophecy of the spiritual conquest of the world through Jesus the Messiah. The name Joshua is formed from the root of the Hebrew word for "salvation." In Nehemiah 8:17, Joshua is written as יֵֵשׁוּעַ or Yeshua, the name for Jesus. Indeed, the Book of Joshua in the Greek Septuagint Old Testament is entitled Ἰησοῦς (Jesus)! Both Joshua and Jesus mean the same - "the Lord saves."