Oracle provided User Guides are best one to read and learn.
You can download from oracle online library.
http://docs.oracle.com/cd/B34956_01/current/html/docset.html
by
Muhammad Hasan AVD , Technical Consultant - Oracle Apps , Arowana Consulting Fz LLC
Best books are guides given by Oracle University, both user and activity guide. If you don't have access to guides next best option is of reading blogs.
Cheers!
you can use youtube for specific module and you can use the following like where you will find all modules documentation is very helpful i use it
before do any thing you have to decide what is the module you want to learn it and decide as technical or implementer ok
this is the link :
http://docs.oracle.com/cd/B34956_01/current/html/docset.html
good luck
