Don’t Make Me Think by Steve Krug
It’s always good to go back to basics. While good usability testing and basic behavioral metrics guide the process, a design has to have a base starting point. You want to hand a group of customers a design that’s got a solid base in behavioral paradigms. That’s what Krug offers.
While many designers will find the book filled with “no shit, Sherlock” points, it’s often those points that we either forget or need to communicate to the team. I’ve always thought of this book as a map of a familiar but always surprising landscape.