This book has seven chapters:
If you're a Perl programmer who is completely new to Perl 6, you'll be interested in this book to get an idea of what it'll be like to work with Perl 6, why we're making the changes we're making, and how the project is going. You'll want to read the first four chapters. If you think you might be interested in getting involved in implementation, read the rest as well.
If you're already involved in the Perl 6 project, you'll be interested in this book to see how all the pieces fit together, and you may want to use it as a reference while you're working. If you've been involved only on the language side or the internals side, you'll also get a chance to see what the other half is doing. In this way, the entire book is relevant to you.
If you're interested in implementing another language on top of Parrot, you'll want to skim through the Parrot information in Chapter 2, and then skip straight to Chapter 5 and read from there.
If you're not involved in Perl but just want to see what the "Perl 6" buzz is all about, you'll want to read Chapter 1, Chapter 3, and Chapter 5. You'll get an overview of what we're doing and why, without all the nitty-gritty details.