The book covers use of VirtualBox under the Debian-based host and guest operating systems. The scripts and examples are based on and tested with Ubuntu 14.04 LTS (Trusty Tahr) running both on the host as well as the guest. Scripts are transferable to other Linux host and guest operating system, however they may require some changes. For Windows and Mac operating systems, read the scripts to guide you through the steps to follow.
This book enables you to manage VirtualBox server using command-line. You can maintain your server remotely without using GUI, although it does not prevent the use of GUI. The guest operating system can be GUI (if that is what you require to virtualize) as VirtualBox provides a remote desktop feature for GUI guests.
The GUI is not described here as it is straight forward to understand and the GUI offers a subset of VirtualBox features. The power to using and maintaining virtualization is in the command-line. For more control and automation, you may have to use VirtualBox SDK/API programming. The book does not enter into the VirtualBox SDK realm and is limited to command line.
So in summary, the book is not filled with pages of screen-shots, rather a set of command options and scripts to maintain a virtualized infrastructure. The book provides script templates to create, clone, backup and manage with automation of several VirtualBox functions.