Yes, the book is written in a tutorial style.
To answer your second questions, a sandbox refers to the fact that JavaFX Script programs run on a JVM in an environment that protects the client machine, requiring the user to authorize actions such as file access.
By the way, my "Helping you become a JavaFXpert" weblog at
http://JavaFXpert.com has lots of information about JavaFX, including the latest happenings. Today's post (April 1, 2008) in that weblog, by the way, contains a link to the video of one of the JavaFX Script presentations that I did at JavaPolis last December.
Here's a direct link to that post.