I like to review about this e books which is talk about VirtualBox 3.1. This is must have book to a beginner of virtualization on their system and also valuable for experience user of VirtualBox. This books cover all about virtualization even you are Windows or Linux user. You can read a sample chapter of it from here.Some review about this book,
It have 8 Chapter which is include,
Chapter 1: Getting to Work with VirtualBox
Chapter 2: Creating Your First Virtual Machine: Ubuntu Linux
Chapter 3: Creating Your Second Virtual Machine: Windows 7
Chapter 4: Installing Guest Additions and Advanced Settings
Chapter 5: Storing Data in VirtualBox
Chapter 6: Networking with Virtual Machines
Chapter 7: Using Virtual Appliances
Chapter 8: Managing your Virtual Machines from a Remote Computer
There also some quiz that can test your understanding of the article on each chapter that you have read.
So, if you interested of this book, you can get it from HERE.