I really like reading Dietrich Bonhoeffer. I have reviewed two different biographies (Schligensiepen is better than Metaxas) and Life Together as well as an Eastern Orthodox version (A Life Together) and an exploration of Bonhoeffer’s Christ-Centered Spirituality, but I am by no means a Bonhoeffer expert.
I have read Cost of Discipleship (although not recently), so I might participate in this online discussion of Cost of Discipleship. It has just started, so you are not behind.
If you do not have a copy of get the new translation which is back down to $9.99 in kindle version. It is titled Discipleship (which is what the original German title was.) The older translation is the same price, so there is no reason not to get the new version.