I'm a psychologist by training but I developed a real passion for computers in the last 3 years (and hoping to reconvert in that field). The purpose of this site interests me greatly, and I've already had quite a lot of fun building the logic gates in chapter1.
It's quite challenging but it's worth it. For me, understanding computers at a low level and building upwards is an important step towards becoming a better programmer and be more knowledgeable in general.
I must say it's quite the challenge explaining this to people, some of which even are experienced programmers. I feel you will never get the complete picture without knowing what happens under the hood - at some level.