It tells lots of things but you can takeaway a few things.

One of the key takeaway example for me was that if you make an approachable flat surface, people will put things on it. This is a small example but tells a lot about design of common things.

Another was that I shouldn't be blaming myself for failing to use an everyday thing, I should be blaming its design.

After reading the book I now keep seeing so many design flaws in so many things around. It also made me appreciate good design similarly. I probably think a bit more about users of code etc now, doesn't mean I write better, but it has changed perspective quite a bit.