As an introductory text, it's a good one; Polinsky tends to organize his presentation around well-chosen examples, and his discussion is usually pretty clear and accessible. Moreover, in apparent contrast to Miceli, he doesn't invoke much mathematics even of an elementary sort.

But that mathematics is clearly lurking just beneath the surface of the words, and I caution the reader that Polinsky will be much easier to read if you've got some math background. (I don't mean graduate-level stuff; high-school algebra will likely be enough, and a little calculus will probably help.) This is a matter more of style than of substance; readers accustomed to dealing with mathematical texts will just be better equipped to worm their way into Polinsky's clear-but-dense prose and get his point.

In coverage, Polinsky's book is pretty close to Cooter and Ulen's, but Cooter and Ulen are probably much more accessible to the typical beginning reader. Despite the absence of explicit mathematics, I'd personally rank Polinsky closer to Miceli in terms of difficulty; if Cooter and Ulen are "elementary" and Miceli is "advanced," then Polinsky is "high intermediate." Your mileage may vary.

Another thing I also like about the book is its price. While I would favor Cooter & Ulen's book on Law & Economics if I was going to use any text in the universe for an introduction to this topic, this book is almost as effective and significantly cheaper. Therefore, if you are Prof considering a book list, remember that college kids have to find the money somewhere. If you are a normal reader, this is a good place to start for the buck.