This month Bonhoeffer for Armchair Theologians is free in Logos Bible Software. You can find it here.
Here is part of the product description from Logos:
This volume in the ever-popular W. J. K. Armchair series turns its sights on contemporary theologian Dietrich Bonhoeffer (1906–1945). Born in Breslau, Germany, Bonhoeffer led quite an intriguing life. This book, with dozens of illustrations by artist Ron Hill, highlights Bonhoeffer’s background and theological education; his time at Union Seminary in New York City; his involvement in the resistance movement against Adolf Hitler; and his participation in the plot to assassinate Hitler.
Words on the Word 