Krug introduces himself as a usability consultant. For those who don't know what that is: clients sent him things such as web sites and mobile applications that the have designed, and his job is to flag things that may be confusing to the people they intend to use it.

Sometimes, he gathers his information by testing things with people in a lab setting to see where they get stuck. A great many times, he is able to tell at a glance where the problems will be without having to recourse to an actual test.

The product of his work is that he makes things easier to use - which is win-win, as a business wants customers to use their web sites and mobile applications to do things like order products or get help, and ensuring these experiences are usable is critical to enabling them to succeed.

Every development team could benefit from the help of a usability professional to help them deliver a product that is usable to its intended audience. However, there simply aren't enough usability professionals to go around.

(EN: This is a bit kind of him. The truth is that many businesspeople simply do not recognize the value of usability - they want to go faster and save budget by not taking the "extra" step of testing and improving what they deliver, failing to recognize that the money they save by skipping the step is far exceeded by the money they lose by putting out an product that is difficult to use. If business truly understood the value, they would find the budget to offer attractive salaries and training to have adequate staff to do the work, and budget into projects adequate funds and time for doing the work - and would gladly do so recognizing the immense return on this investment that comes from putting out a product that people enjoy using, use more often, and recommend to others.)

Those who feel they cannot afford to hire him, or someone like him, can apply the knowledge in this book to turn out better products. Design professionals who work for such firms, and cannot convince them to hire usability consultants, can leverage this knowledge to avoid many of the common mistakes that undermine usability.

Fortunately, usability isn't difficult - it just requires taking time and being attentive. Much of it is simply common sense that is ignored in the heat of the moment, or for love of a gimmicky idea that seems "cool" as compared to a less sexy but more usable method of doing the same thing.

It's a pretty thin book with a lot of pictures, which should make reading and learning a breeze. But this also means it's not a comprehensive guide to the topic of usability, as there is a great deal to learn, but even applying the most basic of principles should enable many firms to make significant improvements.

Krug also specifically indicates that there are no hard-and-fast usability "rules," only principles and general observations. Each task or product is idiosyncratic, and what works for one does not necessarily work for another. You must consider usability in the specific context of a given user, task, and environment - preferably similar to the ones that will use your product in the real world.

He will also eschew predictions about the future of technology. They are most often wrong, and pontificating about what the future might bring is narcissistic and pointless - and makes an author look very silly when his book is opened a decade later. This is the third edition of this book, and when things change enough he will publish a fourth.

The author focuses this book, like his work, on web and mobile experiences. The "and mobile" is new to this edition, as the second edition was published in 2006 when mobile was still a fad used by few people. The provisioning of mobile services has caught on in a big way, though the actual use of mobile services by consumers is not quite as widespread, and the poor usability of mobile may have something to do with that.

One last thing before he gets into it: usability is defined in various ways, and it is rather ironic that those whose focus is usability come up with such elaborate and incomprehensible definitions of what they do. To get past all the pretentions and narcissistic posturing, here is the author's definition:

Usability's goal is to ensure that a person who has the anticipated level of skill and experience to do a task (and maybe a little less than anticipated) can actually do it without it being more trouble than it's worth.

That's really all there is to it.