The OpenSolaris Bible is an excellent resource, beyond excellent. It caters to all levels, from "beginner to advanced", just as it says on the (back) cover. Few books are as versatile. You can pick this up, having no or only limited knowledge of Unix systems, you can be an expert with another Unix flavor, or you might even be a Solaris administrator looking to become aquainted with some of the newer features.
I'm not new to Unix-type operating systems, I've been working on Unix systems for over 13 years. I am an expert with Linux, proficient with *BSD systems, and have varied experience with Irix and HPUX, but have rarely had the chance to work on Solaris. With all of the wonderful features introduced with OpenSolaris in the past couple years, I've taken another look at this great operating system and have used the OpenSolaris Bible as my guide.
I would recommend this book to anyone looking to run or administrate OpenSolaris, and I would certainly recommend OpenSolaris itself.
My only complaint might be that this book will probably become outdated very quickly, due to the impressive rate at which OpenSolaris is being developed. In fact, just yesterday, a new version of OpenSolaris was released, introducing features not present or discussed in this book. However, this is currently the most updated printed material available today, so you really can't go wrong.