This paper (or short book, as it sometimes feels), tedious as it may be, gives a great view into probably the single biggest aspect of photography that most people never think of: the INSIDE of your lens. I took it in slowly, about 5 pages a day or so.
-What does it mean when the lens that came with my Digital rebel have 11 elements in 9 groups?
-Why does a lens need that many small lenses in it? The black and white enlargers only have 1 lens in them and they make my prints crystal clear!
-What is an aspherical lens?
-Why do all the highlights in the background of my hipster cityscapes (because if i shoot like I don't care, the creativity flows, man) have color fringes around them?
When people say "it really has nothing to do with the lens or the camera, it has more to do with the photographer," I believe it. At least, I believe it up until the point the photographer stops hoping to get the picture they think they want, and starts wanting to get the picture they believe they can make.
Gaussian out of focus highlights on a professionally created celebrity portrait really look different than the nisen highlights of that kit lens. Smoother, just... better looking. Why? The more you understand about your camera, and more specifically, your lens, the smaller that gap between "want to be" and "am" is.