When asked to explain a poem once, Robert Frost replied, "What would you have me do? Explain it in other and less good words?" Rather than use less good words to explain Marketing Sherpa, visit and read it yourself. Be sure to read his interview with Steve Krug. And there is much else here (metrics guides, marketing wisdom, market research and surveying, wireless advertising, and others).
Usability and Technology Evangelist Blog here.
Steve Krug is a usability expert and author of the usability classic Don't Make me Think: A Common Sense Approach on Web Usability. I encourage all who believe in usability to visit Steve Krugs blog. Read it in his good words.
Also read How We Really Use the Web, the 1997 classic by Jacob Nielsen How Users Read on the Web and Growing a Business Website: Fix the Basics First.
Together, they are an MBA in usability.
For an example of good usability in how to make a product, see MAKE: Technology on Your Time.