Question : what is the best book to learn and administrative things on WAS6.1

what is the best book to learn on WAS6.1 and also please provide good links;

Answer : what is the best book to learn and administrative things on WAS6.1

The good news is "There is a bunch of information that is available"
The bad  news is "There is a bunch of information that is available"

  It all depends on what you know.  If you are new to WebSphere, then the fact that everything is new is going to mean that you have a huge learning curve.

  The online documentation for WebSphere is available using:  http://IBM.com/software/webservers/appserv/was/library

  There are also some good "redbooks" that are available from: http://www.redbooks.ibm.com/Redbooks.nsf/portals/WebSphere
  On that page, there is a link to "Click here to find WebSphere Application Server V6 Redbooks and Redpapers"

  I think I would start with: "WebSphere Application Server V6.1: System Management and Configuration", the PDF for which is available using:
http://publib-b.boulder.ibm.com/abstracts/sg247304.html?Open

Good Luck