Anarchy, State, and Utopia is the most creative work in defense of right-libertarianism that has ever been written. It is unfortunate that much of the secondary literature is uncharitable or misreads Nozick's arguments, for they are actually more subtle and effective than people may believe at first glance.
If you take the time to look through every footnote, you'll realize that Nozick already knows all the objections and solutions, but leaves the reader to figure it out for themselves. He challenges the reader enormously, and he probably knew that there was no point in responding to critics who simply misunderstood his work.
This book should only be read by those with a background in philosophy; it will be confusing and labyrinthine to anyone else.
There are other good libertarianism books out now (like Michael Huemer's Problem of Political Authority), but those are just cogent and intelligent. Nozick is a higher caliber level philosopher (look at his other works, especially in Philosophical Explanations) and is a *genius*. ASU is written by a special and *brilliant* mind, and must be appreciated slowly.
The first time you read it (if you make it through) you might not be so impressed. But the more you learn elsewhere, turn back to ASU, and notice how much deeper your understanding becomes each time. You need incredible knowledge to even begin appreciating and truly understanding what is said here by Robert Nozick.