MyModel: Bug fix
MyController/MyView: Prev button
JTreeGUI: Setup new DefaultTreeCellRenderer
MyView: Change button 'previous' to 'prev'
JTreeGUI: Change tree to use new renderer
JTreeGUI: Create bookData class
JTreeGUI: Change nodes to bookData nodes
JTreeGUI: Check if book is read
Created isRead method to check if the book is read. 
Updated the renderer to use a different icon for a read book