I’m not getting paid by CBD to promote this, but I should get paid!
CBD has a couple excellent resources on Karl Barth for ridiculous prices:
Karl Barth and Evangelical Theology: Convergences and Divergences by Sung Wook Chung, editor (Baker, 2006), $3.99 (retail $32)
Karl Barth & the Pietists: The Young Karl Barth’s Critique of Pietism & Its Response by Eberhard Busch (IVP, 2004), $6.99 (retail $27)
While you are at it, you should get The Best of A. W. Tozer (2 volumes). Also, Ruth Graham’s nice little book, A Legacy of Faith: Things I Learned from My Father, is only $3.99.