How do I go about learning the Najdorf Sicilian? I want to play and learn the Najdorf Sicilian.  I know that white has three main options:

6.Bg5
6.Be3
6.Bc4

But I don't know much more than that.  Furthermore, I want to play the Open Sicilian as white and against the Najdorf play 6.Bg5, so I think for me it's worth learning these variations.

Should I get Starting Out: Najdorf Sicilian?
Probably(I haven't read it) , other options are a video series eg

https://chess24.com/en/learn/advanced/video/a-complete-najdorf-repertoire/najdorf-introduction 

or a more detailed book eg 

http://www.qualitychess.co.uk/products/1/49/grandmaster_repertoire_6_-_the_sicilian_defence_by_lubomir_ftacnik/ 

or 

https://www.newinchess.com/The_Sharpest_Sicilian_2012-p-1523.html.

In general I would recommend the Starting Out repertoires for anyone under 2000 FIDE.