Dear Parag,
Last steps not important - "In the sh404SEF control panel, go to the [By Component] tab
Set bookLibary to [Do not override]."
Plugin will works if you have made two things:
1) You installed SH404SEF component
2) In Joomla Global Configuration set in SEO Search Engine Friendly URLs - NO and in sh404SEF component set Enable URL optimization - YES.
So, after that you will have such URL for example for alone category
localhost/~taras/joomla/index.php/357/showCategory/49/joomla.html
instead
localhost/~taras/joomla/index.php?option=com_booklibrary&task=showCategory&catid=49&Itemid=357
Move in this way, please.