It is pretty old book. It was published in 1988. Computers were much more clumsy and hard to use but at the same time they were changing really fast. Fortunately author picked everyday things as the main theme of the book. You can read about faucets or doors but what you learn in the process will work in every context.
First idea from a book is about blame. When we see some strange faucet we feel stupid for not knowing how to use it, but we are not to blame. Design of the faucet should be blamed, maybe even designer. Our everyday things should be designed to make them easy to use and understand. One important idea from a book is to think about ease of use when we are buying any kind of objects.
It is one of several important factors of great design. Controls should be aligned exactly the same way that things they control. If you want to see it violated look at controls of your burner in the kitchen.
How things look like suggest how they can be used. If you put the button on the page it will make people press it not drag it to some other place on the page.
Watch Inventing of Principle by Bret Victor for this idea in newer form.
Sometimes taking out control and creating constraints will make product easier to use and understand.
Many of the ideas in the book are 'obvious' and 'common wisdom' for me, but still it was really good to read more about them and put them into more precise ideas.
Why I picked up this old book? Mostly because it is on Bret Victor list: http://worrydream.com/#!/Links