Aaron Martínez and Enrique Fernández, a new member of the Navigation team in Pal Robotics, have written a book about ROS. This is one of the few books about ROS in the market. “Learning ROS for Robotics Programming” starts with the basic principles of ROS and finishes with complete simulations of real robots. It covers almost all the aspects you may find in a robot and it also shows how to work with hardware. Furthermore, it comes with examples and source code.
The book is now available for purchase here (http://www.packtpub.com/learning-ros-for-robotics-programming/book), so everybody can start having fun with robotics!