First of all, thanks for the mention! (I wrote Design for Hackers).
I'll just elaborate so OP and everyone else can get an idea of how I approach things when teaching design.
My goal with the book was to "reverse engineer" everything that comes together to make a good design. In my eyes, the factors of design are always the same (purpose, technology, culture), it's just a matter of understanding how they work together.
OP mentions whitespace/margins. I'm such a white space fiend, I did a whole hour-long talk at SXSW entirely about white space. So, definitely my book talks about that. You can get much better at design very quickly if you forget about everything else (fonts, colors, ornamentation) and just concentrate on white space first.
I also do cover color schemes, and how to build them. If you want an understanding of how I approach color check out the article I wrote "Why Monet Never Used Black"[1].
I also write about font sizes & geometry in design. If you want a sampling of those particular thoughts, Lifehacker picked up one of my tips on the font sizes I always use on projects[2].
Of course, there's also my free email course that creature mentioned.
It was a book with a good design, although it didn't help me learn much about design. The references were useful, but I would have liked to be a step-by-step guide (similar to Drawing on the right side of the brain, but for design) instead of a showcase of 'good' design and some side note tips.
The author also produced a free 12 week email course: http://designforhackers.com/