Like many evangelicals, I guess, I'd be warned off Karl Barth long ago. Possibly having something to do with my adolescent theological infatuation with Martyn Lloyd Jones, who dismissed Barth as a liberal and an apologist for ecumenism (see here for a typical analysis, an article from an old edition of Evangelical Times: http://www.metropolitantabernacle.org/Sword-And-Trowel/Sword-and-Trowel-Articles/The-Significance-of-Karl-Barth), both gross over simplifications, by the way!
I've been mulling over his theology of the Word of God over the past couple of days. He argues for a threefold doctrine of the Word of God: preaching or proclamation, scripture and revelation are argued to be three unified forms of the Word of God - written scripture being merely a human witness to the risen Christ. While I'm not sure I'd go that far, his stress on the dynamic Word of God is certainly something that does more justice to the interplay of Word and Spirit in the proclamation of the Gospel, than many more obviously evangelical formulations. Barth writes that preaching may become the Word of God, not through anything we do, but through the sovereign action of God and his direction. I'm not saying I agree entirely, but maybe Barth was onto something here?
Anyway, I'm exploring Barth further and have started reading an excellent volume of essays by a group of evangelical scholars who engage with various aspects of Barth's theological position. Its Sung Wook Chung (ed.), Karl Barth and Evangelical Theology: Convergences and Divergences (2006), and is well worth careful consideration. I did also come across an IVP volume on Engaging with Barth: Contemporary Evangelical Critiques (2008), which might be worth a look too. There's also the new volume on Barth's influence in Britain: Densil Morgan, Barth Reception in Britain (2010), which is as much about the history of theology in twentieth century Britain as it is about Barth himself, so it'll be a must read as well. But I've enough Barth to keep me going for a while . . .