I administer our CVS server at work. We use CVS in the traditional way, to manage source code from a group of people working together on multiple projects. Before this book, I didn't have a single reference that explained all the basic functionality of CVS. Now, when someone has a question, I can pass along this book for a quick answer.
Most of the things you'll do with CVS are covered in sufficient detail in this book. I do agree with the reviewer who mentioned this is not the perfect reference for some tasks - like merging branches. This book will, however, give you all the background information you'll need so that you can effectively research complex topics like this on the web. The title is appropriate - 'essential CVS.' It's not 'everything there is to know about CVS' - and that's a strength of the book. It makes it small enough that the average developer can read the 'quickstart,' and have a basic understanding of how things work. They can then use the more detailed chapters to gain further information. Only the CVS administrator will need a little more. Even for them, this book will be a handy reference.