Is Yahweh a Moral Monster? The New Atheists and Old Testament Ethics by Paul Copan is an interesting read.  You can find it in both HTML and PDF formats.  The abstract reads:

The new atheists (Dawkins, Dennett, Harris, Hitchens) level arguments against Old Testament morality as primitive and barbaric, presumably undercutting belief in the biblical God (Yahweh). Yet the Old Testament presents creational moral ideals in Genesis 1-2. Because of Israel’s embeddedness in the ancient Near East’s harsh, morally-problematic social milieu, Old Testament legislation is in places still morally inferior, though offering dramatic, incremental improvements upon such conditions. Mosaic Law attempts to regulate and limit tolerated structures (warfare, polygamy, patriarchalism, slavery), permitting various social structures because of human hardheartedness. Though falling short of the divine ideal, Mosaic laws often point to it.