We covered the Book of Joshua in our Bible study last night, and I'm just going to share a few of my thoughts here. No time for a detailed chapter by chapter breakout this week.
First off, I don't see a morally significant difference between the Joshuaite concept of herem and the Mohammedean concept of jihad. Both are essentially holy wars of conquest, fought in the name of God and justified by the idea of divine sanction.
Secondly, this is a surprisingly earthly book with far more talk of bloody conquest and real estate transactions than piety, and when it does touch upon matters of personal piety it often confounds it with the disposition of personal property, as in the case of Achan.
Finally, we still haven't seen much in the way of moral progress so far. Kill everyone and destroy everything is still the rule of the day, whether applied to entire tribes (Hittites, Amorites, Canaanites, Perizzites, Hivites, Jebusites, along with the peoples of Jericho and Ai) or when applied in cases of individual justice (as in the destruction of Achan along with all of his wives and children and property). I suppose this is to be expected when morality is reduced to "whatever the priests tell us that God told them" as opposed to having to reason out for ourselves which actions will have desirable consequences.
When it comes down to it, it is really hard to believe that people can read this book, ponder it for a bit, and still somehow come to believe it was ultimately inspired by someone who loves everyone.