Many years ago I chose this book because it is one of the most popular introductory microeconomics textbooks, and for good reason.  As someone who is not an economics expert, or even a college student taking an introductory Econ class, but just someone who wanted a better understanding of some of the basic concepts of microeconomics, I found this book to be extremely valuable.  (I bought a used and slightly out of date copy for about $20.  I see that the new cover price is over $100 - I don't think I would consider it as valuable at that price!)

There are a lot of critiques of this book online, and with good reason.  This is an introductory book, with all that entails.  It presumes that the reader does not have an in depth knowledge of either basic economics concepts, statistics, or higher math.  Therefore, the language that it uses, the examples that it gives, and the background that it provides is fairly limited in scope.  In order to present microeconomics concepts to the layperson you have to strip out a lot of excess information, and what often gets stripped is a background into the controversy and alternate interpretations of the issue at hand.

In other words, basic textbook is basic.

Principles of Microeconomics may give a limited picture, without a lot of alternate viewpoints or background information, but sometimes that is just what you need.  Microeconomics is the study of how economics affects our everyday lives, which I would argue is something that every person should understand.  It's part of how life works, and it's valuable to understand some of the underpinnings of our basic human motivations and decisions.

It seems churlish to chide Principles of Microeconomics for being basic, since it is meant to be a basic textbook.  It excels at giving real world examples for all of the theories that it introduces, and including diagrams and illustrations whenever they are helpful.  

Other people have criticized Principles of Microeconomics for stating the author's opinions and beliefs as if they were facts.  On this count I cannot comment, but I think it bears keeping in mind.  Microeconomics is a contentious issue, and (as with psychology or art) there are very few things which can be assumed to be solid scientific facts.  Given the same set of evidence, ten economists can easily come up with ten different theories to explain the results.  

As such, it is worthwhile to note that Mankiw was a top advisor to George W. Bush from 2003 to 2005, and critics (according to Wikipedia) describe Mankiw as being "in thrall to the Bush administration."  This is probably a little harsh, but it bears keeping in mind as you read Principles of Microeconomics.

That being said, I would definitely recommend this book for anyone who wants to choose their first book on economics.  I have found its principles and explanations helpful in almost every aspect of life, even before the economy imploded and we all got thrown into Financial Theory Boot Camp by the nightly news.