The rise of tablets and smartphones of different sizes in the last few years brought up a bunch of new problems for frontend developers. In the past most developers and designers used fixed width in their designs, but these layouts break on small devices. Instead of developing a own layout for each device Ethan Marcotte brought us Responsive Web Design. Very similar to Ajax, Responsive Web Design is not a new technique but rather a combination of existing techniques in order to reach a very specific goal: Use the same markup and stylesheets for every device.
This book is kind of the bible of Responsive Web Design. Ethan Marcotte does not only explain how it works, but also why it works and why it is better than separate markup and stylesheets. It is not a book about mobile development (many things like bandwidth and performance are not covered in the book), it is a book how to optimize a layout for every device that exists and how you can optimize the experience using media queries.
Before I started reading the book I already had some experience with responsive layouts, I had read some blog articles and implemented some basic layouts. However, I learned a lot and I can recommend it to every frontend developer out there.
The one thing I was not able to agree with Ethan was how to define the breakpoints of your layout, i.e. when you have to add additional styles through media queries specific to a single device or a group of devices. I will try to outline my thoughts on breakpoints in responsive layouts in another article later today.