There's a literary genre I don't go in for all that much. The Reader. They are usually thick, often heavy, dense with text, and many of them are compilations of lots of bits often uprooted from context. But there's no doubt they have their uses, providing they are edited by someone who knows what they are doing, remembers who the reader is, and who the Reader is for, and knows the field well enough to include not only the important bits, but the interesting bits.
Not long ago I bought the Bonhoeffer Reader, edited by Clifford Green and Edward De Jonge. Yes it's thick, heavy and dense with text. The selections are organised chronologically but also thematically, from student years to final imprisonment. I have most of the volumes of the Dietrich Bonhoeffer Works in English, and almost all that is in the reader is taken from those texts.
I also have A Testament to Freedom edited by G Kelly and E B Nelson, a volume that has served Bonhoeffer students as a core resource for nearly 25 years - goodness is it that long. I remember buying it and some of the times I've lugged it around to have something substantial to chew on. It too combines chronology with thematic organisation. When there's a large amount of material, and you don't have time to read it all, but you want to encounter the significant, interesting, mind expanding, characteristic thought of someone who interests you, a well edited Reader is a good deal. Sure it isn't the same as reading a thinker's entire corpus, though you'd have to ask why do that anyway. But with Bonhoeffer a substantial, discerning, well arranged reader works, and works well. So much of Bonhoeffer's corpus is occasional, fragmentary intimations of an intense life, lectures, letters, sermons, and only a few book length items. Even several of them are made up of reconstructed fragments.
The Collected Works has thousands of pages of biographically arranged letters, relevant contextual papers, and other written material from the pen of someone whose life and thought was compressed into such a relatively short life. Not many will want to plough through them or go to the expense of buying them. So between them, these two readers give a wide selection, with quite a lot of overlap - the most recent of which is, of course,based on a critically grounded text. So those who are looking for a way to engage seriously with Bonhoeffer, and to do so beyond the core gifts he left the church (Life Together; Psalms: Prayer Book of the Bible; Discipleship; Ethics), are well served by these two hefty volumes, printed 25 years apart. having used both of them a bit now, I still like A Testament to Freedom. Reading Bonhoeffer on a daily basis for a few weeks is like training for a 10k of the mind, and heart. Either of these books would do.
Then there's always A Year With Dierich Bonhoeffer. I have to say I've often smiled at the likely response of Pastor Bonhoeffer to the thought his writing would one day be a daily devotional. But reading Bonhoeffer is an exercise in expansion, deepening and toughening; expansion so that devotional isn't about a theology of my fulfilment, but a theology of the cross; deepening because for Bonhoeffer devotional is a word redolent of sacrifice, cost, consequence and daily dying; toughening because everything Bonhoeffer wrote that has enduring value for the Church is a distillation into words of the experience of confronting, subverting, challenging and having to live under the oppressive controls of National Socialism. The July 24 reading has these words: " The people who love, because they are freed through the truth of God, are the most revolutionary people on earth. They are the ones who upset all values; they are the explosives in human society." Not for Bonhoeffer the chronic niceness that avoids confrontation and calls it peacemaking!