The book of Joshua is the first book that wasn’t written by Moses. In fact, Moses—who is the man the Israelites considered to be their greatest leader, against whom future leaders would be measured—has left some pretty big shoes to fill, and that was probably somewhat intimidating for Joshua, his replacement. Or at least, it would have been, if Joshua had to do it on his own. But if God was the Israelites’ true leader, and all Joshua had to do was faithfully follow Him, then there was nothing for him to be worried about. Based on the evidence, I think Joshua did very well.
This period in the Israelites’ history represents a high point for them. In fact, I would say that it’s probably one of their highest points, in terms of obeying the LORD and following His commands (although a good case could be made that the Israelite nation under King David might have done just as good or better).
This book is concerned with the Israelites taking over the Promised Land, and destroying the nations who had previously lived there. Although the Israelites didn’t do a perfect job—and we’ll see the results of that as we move into the book of Judges—they did do a pretty good job, and I believe that, for the most part, they were at least trying to follow the LORD.
You’ll also notice that Joshua himself is not mentioned that much, in the book. (At least, not when compared to how present Moses was, in the last few books.) Personally, I think this is a mark of good leadership, on Joshua’s part. He knew to get out of the way, and let the LORD rule His people. (Not that I’m saying that Moses did badly in this respect, mind you. But with the Israelites taking over the Promised Land, and becoming a warring nation, it was good for them to remember that it was the LORD who was winning their battles, not their leader Joshua.)