There is so much richness in the first forty pages of this book that I cannot possibly address all of the issues Kierkegaard has brought up, but I will do my best.
Like John, I see the critique of Kant and Modernism very clearly: If reason can nihilate everything, then what is left? For Kierkegaard, reason is irrelevant - reason is only possible in the realm of the earthly, the finite. In terms of the spirit, or infinite, reason has no place. So we are left with no reason, and no substitute for reason. Faith is not a substitute for reason because faith is highly personal, subjective, and not rational. It rests on the absurd, rather than the actual, and, because the absurd can only be verified by God, and belief in God is unverifiable itself, faith is no substitute to the promises of reason, even if this reason is not truly reasonable (or actual). Thus, all we are left with are shambles of paradoxes lying at our feet. So Kierkegaard looks for an example, and exemplar, and he finds Abraham, and becomes even more confused then ever. For the faith of Abraham is not mere naivety - it is careful, sincere, and full of doubt and anguish. And this is what makes Abraham a knight of faith - we see what Abraham did, we know who he was, and yet, we haven't the slightest clue as to why or how to get to his point. It is at this point that the crisis becomes greatest and the critique of Hegel blatant - We cannot "know" God, or the Absurd, we cannot quantify faith, and we certainly cannot ascribe values or notations to "World-Historical Individuals" if we do, as Kierkegaard points out, it is not because God has anything to do with it, but because we ascribe a certain value to it - to Kierkegaard it is Hegel who is taking the easy way out, because in a Hegelian system faith is cut out of the picture all we get is: Spirit, and how it manifests itself in the world, regardless of whether or not we choose to believe in it. In this sense, we lose the anguish, despair, and beauty that is faith.