...books?

Give your self a goal,lets say try to connect different nodes using MEL script...
Try creating the window with buttons that will create some poly primitives..
Try to setup a rotation order of 3 cubes so when one rotates other will rotate half the rotation as last and other will translate.
You'll see, you will search for some other syntaxes that will help you in your job.

I think there is a good web site describing MEL, try in google!

MEL that!!!