After reading some of the other responses, I've gone back and reflected on my answer. I'm forced to agree with others that this book may not necessarily be the best starting point for some individuals.
In my case, reading Friedl's book reminded me of a senior level computer science course that I had to take (Formal Languages and Automata). While taking the course, I struggled to understand how the concepts would apply to programming. Friedl's book connected the dots in my mind.
Regardless of your starting point, I'd recommend doing some experimenting on your own. At least for me, I couldn't fully wrap my mind around regexes without actually doing some hands on learning.
