I already have all of these in real books, but it is a very good introductory special for those who want or like digital versions. There are selections from across the decades of Barth’s career, from the early 1920s through to a few final pieces from shortly before his death in 1968. Some of them are major works – The Münster Ethics (1928), Barth’s Gifford lectures The Knowledge of God and the Service of God (1937-1938), and Theology and Church, a collection of essays from 1920-1928. Others are occasional pieces, including lecture series, sermons, short theological pieces, and Barth’s tribute to Mozart, with whom he carried on a life-long love affair. Also included in the set is the massive biography by his friend and student Eberhard Busch, which I have reviewed in three posts under the title of Karl Barth, A Remarkable Life.
The books are available from Logos.