The book is suitable for all three, however I would have difference advice depending on your level.
A beginner should read more than this book to prepare them - I would relate this book to a study guide before a test. Its true value comes from supplementing your knowledge and making sure that you've covered all of the topics mentioned. If you are a true beginner, I would first recommend a book like Head First Java, which goes into depth about the topics and explains them with great visuals. Then, I would recommend reading this book to summarize and prepare you with the interviewing aspect.
An intermediate or expert would find more value in reading this book and then using Google to do additional research on any topics that they may feel shaky on. Being able to answer (and understand!) all of the questions in the book is a great way to inspire confidence before an interview.