Reformedforum.org recently published a list of 5 important books to help you understand Barth. Only one of these is currently available in Logos. These lists are always subjective but would like to see the other four titles in Logos format.
http://reformedforum.org/5-books-barth/
The quick version is as follows:
- George Hunsinger – How to Read Karl Barth.
- Bruce McCormack – Orthodox and Modern.
- Eberhard Busch – Karl Barth: His Life from Letters and Autobiographical Texts.
- Cornelius Van Til – Christianity and Barthianism.* In Logos Format
- Richard Burnett – The Westminster Handbook to Karl Barth.
And if you haven't already signed up also check out
T&T Clark Karl Barth Collection (9 vols.) and Thy Word Is Truth: Barth on Scripture by George Hunsinger available as a standalone resource or part of an Eerdmans Collection for more on Karl Barth