Before critiquing this book, Mr. Walzer should be given some credit. He manages to make a good argument for pluralism, equality, and the like, and avoids the deus ex machina thought experiments a la Rawls (with "original positions") or the like. For that, Mr. Walzer should be thanked.
Now for the problems. Walzer, author of "Just and Unjust Wars" and "On Toleration" (among many others), is trying to defend a certain order of society where differences can be accepted and equality may be ensured. But Walzer's arguments suffer from a major problem - his starting point(s) are left undefended, and indeed sometimes even undefined. The key to his system is "shared meanings," an idea that he has used in other works (like "Just and Unjust Wars" [J&UW]) under various names. What these shared meanings are, Walzer generally avoids saying directly. As he mentioned in J&UW, Walzer tends to avoid the more complex questions of the foundations for morality and the like - he tends, in practice anyway, to be an antifoundationalist. This presents a problem - he gives the reader all these beautifully reasoned arguments for his idea of society, but always leaves the starting-point out. As such, it is hard to make much of his argument, if you may find yourself in disagreement with his elusive first principles.
Walzer argues that he's starting with "shared meanings," and just following out logically what that entails. In practice, this results in a social democratic, left-oriented society. Fine. But one feels a sleight-of-hand is being played. The "shared meanings" are rather vague. Moreover, "shared" by whom? While Walzer gives some discussion to this, the question lingers. Shared by all those in Western society? By those in only one country? By those in one class? By those on the editorial board of "Dissent" magazine? The reader may find that s/he is locked into the "logical result" of premises that were unknown in the beginning.
Having written all that, this is a very important book in political thoery/philosophy. If those are areas you are interested in, you should read this book. While well-argued, I find it less than compelling (for the reasons discussed above). I could be wrong. Read and decide for yourself.