Humans are "Hard" because they are individuals with their own motivations, drives, capricious emotions and in a word, are not always "rational". I feel most of the books on management/organizations/communications, approach Human Communications from a utopian viewpoint. They assume a path of least resistance and then impose a structured process (fad of the month) to arrive at a positive end goal. I have come to the conclusion that this is all unworkable BS (note books like "Leadership BS", "Bullshit Jobs" etc.) and we need to change our approach completely based on actual realities rather than wishful thinking. To that end i found the following books useful;

The Art of Worldly Wisdom (aka The Pocket Oracle and Art of Prudence) by Balthasar Gracian - A set of aphorisms with penetrating insight into Human Nature.

Why we do what we do: Understanding Self-Motivation by Edward Deci - A short book from a psychologist.

The Empowered Manager: Positive Political Skills at Work by Peter Block

Management: A Political Activity by Ted Stephenson