Consider this book the Definitive Reference for PowerShell. Written by one of the designers of the PowerShell environment, the author knows all the ins and outs, back-alleys, hidden rooms, and secret handshakes the language offers - and isn't afraid to grab you by the hand and drag you along (like it or not!) for the tour of your life.
Therein, however, is the reason I can't recommend this as your first PowerShell book. The book is very logically planned out, the information very well presented in relatively easy to understand language, there is an abundance of script snippets to demonstrate what is being talked about, and the writing style itself is entertaining to read. But the author knows too much on the subject, and like any proud parent, often "too much information" is given, delving too deep into the gears and cogs of PowerShell and the underlying .NET framework for the (often basic) building block component, which might overwhelm the new PowerShell user, especially if the user does not have programming, let alone scripting, experience.
So although I say don't make this your first purchase, make it your second - and probably your last. Start with an "Introduction" style book (like Microsoft Windows Powershell Programming for the Absolute Beginner) to get used to the complex environment (even if you've only had VBS/JS experience), get comfortable with the basics of the shell, then move up to this title. You'll soon find out that every aspect you thought you knew has much more to the story than you thought, and you'll walk away from this read able to do just about everything you want.