Can't access WD My Book Live from different network

No, you don’t need to be on the same network in order to access the my book files. Check the link below for the steps.

http://wdc.custhelp.com/app/answers/detail/a_id/7080/session/L3RpbWUvMTM0NjUyOTcxMS9zaWQvNjVSSUdhNWw%3D