This book has been tested on people who didn’t even know JavaScript. They were able to pick up Vue by reading the first chapter! Going forward, you will find concepts that are more and more advanced and, even if you are familiar with Vue 2, you will probably find some trick you didn't know about or some wise suggestion that will help you along the way.
This book, if followed from cover to cover, will turn you into a proficient Vue developer. On the other hand, if you already are, it provides a good reference for many different features and techniques that may come in handy from time to time. Finally, this book is also a valid migration guide if you have already experimented with Vue 1 and you feel overwhelmed by change.