So if you need an accessible introduction to Barth to go with your new set of Church Dogmatics, I've got just the thing for you: the impressive and delightful Welsh theologian Densil Morgan has a nice new volume, The SPCK Introduction to Karl Barth (SPCK 2010), 116 pp. (also available from Amazon UK).
Here's an endorsement I wrote for the back cover (along with endorsements by Oliver Crisp, John Webster and Tom Hastings):
Barth was an exciting thinker, and the best writing on Barth manages to capture something of that boundless energy and excitement. D. Densil Morgan offers a vigorous, fast-paced narrative that weaves together Barth’s life, his intellectual development, his turbulent political settings, and the overall shape of his theological work. He provides a remarkably clear and concise overview of the whole Church Dogmatics, with a welcome emphasis on Barth’s anthropology and the rich “humanism” of his thought.