Several extremely important design lessons in this book. I had to stop reading and think a few times... Just never thought about things they way Chip and his teacher talked through ideas. But a warning - he has a wicked and almost disturbing sense of humor. One page you'll be laughing out loud and the next you might be a little freaked out.
If you're a designer I'd say you have to at least read the interludes after most of the chapters. They're brilliant.