The cover shows a Post-It attached by a thumbtack, which seems like the result of someone who doesn't understand Post-Its. And the Post-It has a smile drawn on it. Oh no—is this another management book telling managers to cheer workers up with cheerful little notes and happy-face stickers?
This book's thesis is much more sensible: Workers are motivated when they see that they're getting closer to their goals. If they do something useful and can tell it was useful, they cheer up and do better work. If they hit a barrier, they get discouraged and do worse work. This leads to virtuous and vicious cycles.
In some kinds of work, it's easier to measure progress. A garbage collector can track trash-bins-emptied-per-hour. But what about folks working on more abstract problems? A Gore-Tex engineer trying to figure out a way to get a new coating to cling to fabric can lose sight of the overall goal as they wallow in the mire of details. If you're a manager, it's all very well to motivate with praise and raises and such. But removing roadblocks can motivate even more.