I failed high-school math, and couldn't even spell linear algebra two years ago. I'd never done any game programming to speak of, and had never written any C code before starting Handmade Hero.

After watching through most of the series, and writing a 3d engine (HH style, no libraries), I have internalized an amazing amount; the vast majority of what Casey's gone over. I agree that often times he goes into more detail than necessary - even for me, who started knowing literally nothing about what he was talking about, but I would attribute the amount of learning I've gotten out of the series to exactly that. For someone that doesn't understand the difference between an Object Transform and a Camera Transform, the only way for them to actually learn what they are is to hammer it home again and again - through examples and practice. I think I am exactly his target audience - young programmers who want to learn how to make video games.

Just my 2c