Hadn't heard of The Humane Interface, I'll have to check it out :)
Re: C&C, a couple of things (just picking from my highlights).
Chapter 2 - Consistency & Character
This informed my own work quite a bit. Especially notes about how consistency aids clarity in the product. Also nice "hmm, now there's an idea" type of stuff like "a designer creates an architecture of information within the mind of the recipient of his work." This triggered a bit of a waterfall, leading to stuff like reading Christopher Alexander's _Notes on the Synthesis of Form_.
Also from this chapter is the point about how having a consistent behavioral language. Meaning, if two elements perform similar tasks, they should look similar to one another.
Lots of great little beats like this that have wedged themselves into my thinking.
Chapter 3 - Simplicity
The one about only forcing a user to create an account when it provides value really informed my ability to design solid onboarding experiences. Taught me to build gradually invasive products that speak to the user like you would a new acquaintance. Over time, you slowly get comfortable asking them for more and more (e.g., use things like local storage to persist data temporarily to give the feel of hitting a DB).
---
Man, is there a place to talk about stuff like this? You got my hamsters spinning.