For this essay, you are to analyze Michael Sandels argument in The Case against Perfection and make and argue a claim about it.
Analyzing an argument is one of the fundamental academic moves any scholar makes. In order to analyze an argument, we have to employ the kinds of skills we have been working on so far: summarizing ideas, analyzing evidence and ideas, raising and justifying questions, and so on. Each of these skills will become a crucial component of your essay.
The structure.
When we present an argument of this sort, what does it look like? That is, what sort of structural components must it have?
In order for it to be an argument and not just a collection of observations or descriptions, your essay must first present a question or a problem about the text. That is, before your reader reads your essay, he or she will have to have a good reason to read it a reason that takes the form of a problem, question, incoherency, ambiguity, etc., that you propose to resolve through your argument. Generating a question about the text often involves interrogating its assumptions, pointing out its implications, or speculating about its consequences.

But, remember, we dont just present our questions by themselves a good introduction does the intellectual labor of showing the reader that the question it is asking or the problem it is posing are genuine questions and problems (refer back to Daniel Hemels essay on Lincoln for a great example of how to do precisely this).
A well-structured essay will also take time and space to summarize the text being analyzed.

This means not only that you are pointing out the main ideas, but that you are presenting as well the various good reasons that the author has for having these ideas (for if theyre not good ideas, why do we need an argument to debunk them? Why bother?). That is, before we can trust your analysis of an argument or a text, you have first to show that you thoroughly understand its ideas, the ideas behind the ideas, etc.
The bulk of your essay, however, will be devoted to analyzing the argument presented by Sandel. You need, for example, to show how the kinds of examples, evidence, and logic he uses lead you to make your argument.

Thus, if your argument has something to do with, for example, false causal connections between different elements of Sandels claims, your analysis of the evidence has to show that this is truly the case. If your argument has to do with erroneous assumptions (about the way human nature works, the way society functions, or whatever), your analysis of the evidence has to show that this is the case. If your argument has to do with showing that there are deeper consequences than Sandel acknowledges, you have to show how his ideas do indeed lead to these consequences. And so on.
The goal.
What should emerge from your essay? That is, after having read your essay, how should your reader have been moved from what he or she thought before having read your essay?
You should have presented an argument that makes a point about the text that is not obvious for if what you are arguing were obvious, why do you need to argue it? You should have, that is to say, made an argument that feels like an argument, and not just a restatement of the (obvious) facts of the text itself.

Instead, your argument should have done some intellectual work in making what was perhaps initially unclear about the text or its claims clearer, or the intellectual work of showing how something superficial about the texts claims needed to be deepened or made more complex or sophisticated. Or, again, your argument might have shown us how something ignored or made tangential is actually central or significant to the issues at hand.

In any of these cases, your goal as writer of this essay as is your goal generally as a scholar and thinker is to have helped your reader come to a better understanding of not only the text, but also the issues with which the text is dealing. In other words, you should have taught us a new way to see or understand Sandels argument.