If you're new to building web applications and want a balanced perspective on the engineering challenges involved -- from understanding user needs to data modelling to scaling gracefully -- this book is a great place to start. It's mostly language-agnostic, so it'll be a good starting point for a few years but won't update you on the latest technology. Nevertheless, I know very few web developers who wouldn't learn something important from a careful reading of this book.
Where this book really shines is as a bridge from the world of college Computer Science to the world of actually building applications people use. This transition encompasses understanding your users, making flexibile designs, considering security, aesthetics, and a host of other issues one does not actually learn in a normal college CS curriculum. Thanks to its project focus, this book (and the course curriculum it implies) seeds an awareness of these many issues that can later be developed through experience. Other "software engineering" books over-emphasize theories, but this one will actually press you to get stuff built.