How I can add new fields in the books?
For example: author's email, author's website, color or B/N, etc.
Hi ramon51, this is a very challenging customization, because you need to modify various files in various folders.
In this customization you need to change the view , the model and so on, in frontend and in backend side.
Then i suggest you to start to read the official guide of joomla on how to create a component.
You can start from here (the 1st part): [url]http://docs.joomla.org/Developing_a_Model-View-Controller_Component_-_Part_1[/url