Anonymous. Jewish tradition names Joshua for most of it.
When
The events are placed in the late second millennium BC; the book was compiled later.
What it is
Crossing the river, taking the land, and dividing it between the tribes.
What to watch for
The conquest is told as complete in the summaries and plainly incomplete in the details, and the book lets both stand.
But if it is unpleasing in your sight to serve the LORD, then choose for yourselves this day whom you will serve, whether the gods your fathers served beyond the Euphrates, or the gods of the Amorites in whose land you are living. As for me and my house, we will serve the LORD!”Joshua 24:15