As a user experience designer with 10 years of experience and clients like National Geographic, Stephen Hawking, Best Buy, Bon Iver, and Harvard University, I have experience with nearly every method described in this book. Yet when I pack up to go to work or consulting gigs or client meetings or lectures or workshops, this is the first book that goes into my bag before I leave home. When I'm not carrying it with me it is usually still close at hand. There are many more inspiring, industry-changing texts on the market, but Universal Methods of Design is simply the most valuable book in my day-to-day practice.
I thought of saying that this book is to user-centered designers what Strunk's Elements of Style is to writers, but the analogy isn't quite right. Writers generally know the best practices for semicolon usage and unordered list formatting. In contrast, most people that claim the title "user experience designer" still spend the majority of their time wireframing or designing in Photoshop. It's really not your fault, it is ours; the UX community has done very little to help educate entering UX professionals, so you have likely never been exposed to most of the methods detailed in this text. You don't know how powerful a simple technique like Affinity Mapping can be, or how the investment in LEGO's Serious Play products can yield a hundred-fold return, or how an absurd hour spent writing love letters and hate letters to yourself can significantly improve a product. But for the aspiring UX designer, this book is an essential introduction to the methods used in professional experience design projects.
For those of us that have experience with these design methods: we all have dealt with those challenging projects, difficult stakeholders, or unique product requirements that seem to exhaust our standard design toolbox. Those situations where our usual methods for scoping, defining, researching, modeling, prototyping, producing, and testing seem inadequate. In these situations, there is no better reference than what Hanington and Martin have put together in this book. Buy it, and if you are underwhelmed then I'll buy you a drink and let you hassle me about it when I see you at the next conference.