The first thing I noticed when reading this book is how familiar it all sounds. This book was published before World War II and it has been thoroughly absorbed into our culture. The principles he outlines seem patently obvious these days.
Since these principles are now such a cornerstone of how we do business and interact, they almost sound trite. Like they're part of the problem, these days. I know I've read at least a million threads about bad behavior in public that's aided and abetted by how people and businesses implement Carnegie's principles -- "give people what they want", "don't criticize", etc.
So in some ways, this book reads as a "How to be obsequious and get walked all over" manual because 21st-century people don't react the way the people in his Depression-era stories do.
But I don't think that human nature changes all that much. Not the essential human nature. I don't think Carnegie is wrong, just that the implementation is out of date.
The second thing I noticed was how often I've seen these principles observed, but insincerely and/or by formula. I can't speak for anybody else, but there's so much praise out there and people seem to dole it out so easily that I don't put a lot of value on it. Especially if people use canned, vague phrases. "You must've worked hard on that." "We appreciate your contributions."
We suffer from a certain amount of hyperbole in modern life -- "EXTREME CAUTION!!!" on a cup of coffee. Because of statistical outliers and the horrible stories they generate, we all have to swaddle ourselves in bubble wrap. We're jaded and quick to assume insincerity.
Or maybe that's just me. I don't take the warnings on coffee cups seriously.
From a writing point of view -- and I picked up the book to try to fill out my character Maggie a little more -- it's good to see the principles laid out clearly. And it's good to read his dated stories and ask one's self, "But how would you do it nowadays? How do we show sincerity in a world that's saturated with advertising propaganda?"
Or, "How will they be showing sincerity in a culture that's getting thrown back to its frontier roots?"
How do people demonstrate sincerity in your universe?