Responsive Web Design with Adobe Photoshop
Dan Rose, of Photoshop Etiquette fame, has taken all of his many years of experience in designing responsive websites in photoshop and brought it into a book that we can all learn from and appreciate.
While I believe that you should get into the browser as quickly as possible to test out how the design performs across multiple devices and viewports there is still a requirement to work in photoshop to get some higher fidelity to the designs themselves.
In doing this you often find that designers maintain the same workflow they might have for print when instead a different approach is needed. In this book Dan Rose takes you through that preferred process to benefit both the designer and the developers.