The Subject to learn if you want to go beyond text data type and would like to go for processing related to audio signals.
Great Books are available for this Subject. It requires A Lot of Patience to Understand this Subject.
You can go beyond this Book and Write your own Book on DSP!
Ok, That sounds a little too cocky but The Subject is Great to Learn.
Hold on to Your Horses and Get a Grasp on this Subject Matter.
I wont steal any Shine from the Books, but you can Learn DSP through Books With Ease!