The metaphor of the evolutionary mountain best describes the underlying idea of this book: as we 'descended with modification', our biological features, including those of our brain, were simply engineering feats that were just 'good enough' for us to survive long enough to reproduce to settle at a local maximum, somewhat effective but far from perfect (perfection being the global maximum) - with exceptions such as the human eye that prove to be marvellously designed, except for glitches such as unnecessary blind spots.
The real power of this book is how Marcus extends this evolutionary argument to human cognition, something that gives us a better intuition of how our evolutionary history lead to our brains. However, to most psychology undergraduates - the chapters on memory and pleasure will seem to contain very familiar examples from other books/textbooks (Kahneman, Trversky etc.) that are better classified by
You Are Not So Smart: Why You Have Too Many Friends on Facebook, Why Your Memory Is Mostly Fiction, an d 46 Other Ways You're Deluding Yourself
You Are Now Less Dumb: How to Conquer Mob Mentality, How to Buy Happiness, and All the Other Ways to Outsmart Yourself
that have a more thorough and well categorised collection of biases. Given the short size of this book, however, no matter how oft-repeated the examples are, they are just enough to support his 'Kluge' hypothesis.
Perhaps the most interesting chapters of this book is the one on how Languages and Mental Illness are examples of Kluges. After all, how we stumbling upon tongue twisters is simply an inevitable result of the way we vocalise. Marcus argues that Mental illnesses such as depression are prevalent in populations because evolution disregards its effect on our inner lives in favour of the final result - propagation - something that members who carry genetic dispositions towards these illnesses manage to do by reproducing. It is not because these illnesses necessarily have some adaptive features that allowed for them to be selected but because our mind sits on a local maximum, effective enough for us to survive but still having us run the risk of having glitchy features such as ruminative feedback cycles that result in depression (or mania).
I shouldn't forget to mention that the ability for Marcus to constantly take analogies from Computer Science and Engineering without running into jargon serve as a first-rate way to get a better hold of the idea of the mind as a error-prone gadget. The ideas tackled are deep and compelling yet as evident from the repeated quotations and derivative work in the book, they are not novel or extremely revolutionary - but neither is that something we should always expect from a book, nor does it take away from it being a fun and interesting read.