Is it possible to enhance one's learning ability?
Interventions which try to make a person 'smarter' in pretty much any sense of the word don't really work. In particular, methods very rarely show any spillover effects whatsoever.

However, what can work is the application of good learning techniques.

Most people trying to learn stuff tend to highlight, reread, summarise, or try fancy mnemonics. These usually don't work very well and are more likely to make you think that you know what you're doing than actually facilitate understanding. 

What people generally don't do but what does work are distributed practice, spaced learning, practice testing.