This is a short but profound (and dense) theological study of Genesis 1-3, along with a shorter study on the general theme of temptation. I had to read it twice to get a decent understanding of it, but I'm sure there's a lot that I missed along the way.
Bonhoeffer starts Creation and Fall by noting that the Church, living in the middle of the fallen world between the beginning and the end, can only know of the beginning through Christ who meets us in the middle. When it comes to creation we can only know what God reveals to us through the Word. Thus "It is impossible to ask why the world was created, about God's plan or about the necessity of creation. These questions are finally answered and disposed of as godless questions by the sentence, 'In the beginning God created the heavens and the earth'." From here Bonhoeffer launches into exegesis. His line-by-line analysis of the creation narrative in Genesis 1 bears some similarity to that of St. Augustine's (in Books XI-XIII of his Confessions), but it has the sophisticated philosophical and theological edge that is characteristic of dialectrial theology. The empty void represents the space between God's freedom to create and creation itself - nothing bridges the gap between Creator and created. Even before the Fall God preserves creation, and it is this preservation that condemns creation to its continued sinful existence after the Fall. In creating day and night God sets up the rhythms of creation (not to be confused with the strictly physical rhythm of day and night). In erecting the firmament, God puts in place the fixed and unchangeable aspects of creation, including mathematics; these seem to take on a life of their own after the Fall, thus alienating us from them. After creating life in general, God creates humanity so that, as God looks on creation, God can see the image of God. God's freedom with respect to creation is mirrored in each person's freedom with respect to other people (hence "God created them male and female") - not a freedom from other people, but rather a freedom for other people. "The analogy of man to God is not [the analogy of being] but [the analogy of relationship]".
Bonhoeffer notices a seamline between Genesis 1 and Genesis 2. "In the first account we find man-for-God, here we have God-for-man; there the Creator and Lord, here the near, the fatherly God." Genesis 2 reveals that, for humans, body and soul are one - the two do not exist without each other. Eden is placed "in the middle of the earth", and in the middle of Eden are placed the two trees. These trees represent the limit of humanity - not a limit on the edge of our existence, but a limit in the very middle of our existence. Everything in the story from this point on represents a sort of attack on these trees; with each new event, the risk of humanity placing itself at the center of creation grows. Eve herself gives Adam a tangible way of knowing his own limit, and vice versa; yet rather than strengthening one another in bearing their limits, they lead one another to surpass their limits. The serpent, too, is found inside the garden; the serpent does not come from outside creation but is part of creation. By asking about the actual meaning of God's commands, the serpent does not directly tempt Adam and Eve to disobey God (an impossibility), but rather tempts them to obey God in a new way that God has not revealed to them. They can only understand the lie of the serpent as new truth. Even so, the Fall is uncaused by all of this and is therefore entirely inexcusable. From here, mankind is condemned to live in its own death, to exist because of God yet to be without God. The story of Cain and Abel points to the story of Christ, thus establishing the Cross as the Tree of Life planted in the middle of the world and Golgotha as the new Eden.
In Temptation, Bonhoeffer opens by noting that the prayer "Lead us not into temptation" cannot be understood by either the natural or the moral person, both of whom see temptation as a desirable test of their own strength. But for the Christian temptation means being stripped of one's own strength and being delivered into the hands of Satan - this is something that we can and should pray to avoid. The story of Adam's temptation is paralleled by the story of Christ's temptation, yet "The temptation of Christ was harder, unspeakably harder, than the temptation of Adam; for Adam carried nothing in himself which could have given the tempter a claim and power over him. But Christ bore in himself the whole burden of the flesh, under the curse, under condemnation." In the wilderness Christ is tempted in the flesh, in the spirit, and finally in completeness. On each occassion his only recourse is to the Word of God, no more and no less - unlike Adam, he does not try to go behind the Word of God. Rather than understanding our temptations as being our own, we can understand our temptations as the temptation of Christ in us. To ask why God allows us to be tempted is to ask why God allows Christ to be tempted. The idea of temptation by the devil speaks to the objectivity and external nature of tempation, while the idea that we tempt ourselves speaks to the subjectivity and internal nature of tempation; both points of view are necessary.
What I really love about both of these studies is their emphatic Christocentrism - something that is typical of Bonhoeffer but very atypical of studies about Genesis. For Bonhoeffer, Christ pulls together and brings into focus all the various strands of theology. Thus while these studies are fairly heady and can be difficult to wade through, they also serve an important devotional function by pointing the reader back to Christ again and again.