The quality of recent books on Barth's moral theology, as I have indicated elsehwere with reference to Gerald McKenny's latest offering, is high. As well as McKenny, I have been occupying myself with a new volume of collected essays, edited by Daniel Migliore, entitled Commanding Grace: Studies in Karl Barth's Ethics (Grand Rapids: Eerdmans, 2010). The volume is the published papers of the 2008 Karl Barth Conference, held at Princeton Theological Seminary, USA. I have so far only given light reading to several of the chapters, and must return to them in coming weeks with a more serious eye to the detail of the arguments presented (not least because I'm reviewing it for Theology journal), but thus far I have been enlivened by what I've read and the quality of engagement (positive and negative) with Barth's thought.
The contributors are: Nigel Biggar; John R Bowlin; Todd V Cioffi; Jesse Couenhoven; Timothy Gorringe; Eric Gregory; David Haddorff; Christopher RJ Holmes; Danile Migliore; Paul T Nimmo; Katherine Sonderegger; Kathryn Tanner; and William Werpehowski.
As time goes by I hope to comment further. For now I'll just encourage you to get a copy and read it if you can.