I got a lot of value out of this, and have started using the techniques. Especially valuable, I think, was the way Nick writes about success spirals, and how you really have to apply this stuff in a way that will work — because faltering or half-assing it will just set you up for a harder time down the road if you try again.
Some of the book gets pretty braggy though, which personally I find *de*motivating. If that applies to you too, I'd skip or skim chapter 7 (where he tells an exaggerated tale of doing way more work than you or I probably think possible for ourselves right now), and chapter 8 (where he goes on about how he tried to learn a ton of things, and turns out they were all easy, especially with the help of all the smart, skilled friends who fell in his lap to teach him).
One thing that ate at me about Chapter 8: When talking about how he was reading a book on learning to lucid dream, he comments "even though it's harder than the author made it out to be—after all if he's writing a book on it, then he probably had an easier time learning it than most people will", with a footnote of "A reader pointed out that you should have the same skepticism towards this book and me. Well, this is ironic".
While I appreciate the self-awareness of this footnote, Nick doesn't do anything in this book to deal with this fact. He spends a lot of time bragging about how things are easy once you know how to do these hacks, while very much failing to address the issue that for some people, *this will not be easy*. It makes it much harder to be encouraged by this book, because in the back of my mind, he's sabotaged my Expectancy* by hinting that I probably will never be quite as good at it as he is.
(*Expectancy is one of the core influences on motivation outlined in the book — how likely you feel you are to succeed at a goal)
And finally, one thing I very much wish had been included in this book but was not: What to do with a failure at a goal. He goes to great lengths talking about how to build a successful Success Spiral, you must set goals for yourself that you can and will achieve, and that the consequences for messing that up are dire — you damage your Expectancy for a long time going forward. But inevitably we will fail at a goal at some point, and he leaves us with no hint as to what to do from there.
EDIT: After talking with Nick (I actually work with him, heh), he had a good response to the last point about what to do with failures: You must analyze them and figure out exactly why you failed, and then figure out ways to ensure that you won't fail in that way next time. This might mean changing the goal to allow for circumstances that you had not foreseen (making it a little more forgiving), or changing how you execute your goal. And once you've done that analysis, and you truly believe in your new approach, start fresh with the goal again. Embrace the idea that this won't be like last time, because you've done the work to prevent the ways you might fail, and this time you won't make the same mistakes again, because you've learned and improved from your mistake. And this time you must go into it with a renewed vigor — put twice as much effort into making sure you succeed. Putting in only slightly more won't increase your odds enough.
Doing this analysis and planning for next time, and going at it harder, will help make the goal more achievable, and recoup some of the Expectancy lost by the failure. If you can believe in your updated strategy for accomplishing it, then you can believe you'll succeed where you failed before. But this is not as effective as doing this pre-emptively, and there will be SOME Expectancy hit that you don't recover — so emphasize thinking about this beforehand as much as possible.
One minor example for me I've run into so far: I have a few goals to do a thing 6 out of 7 days a week. I got behind on one of them by skipping two days in a row out of a 14 day total (not technically failed, but below the average target rate) because I was putting the tasks off until late at night when the deadline loomed. So I adjusted to doing them early in the day so I didn't run that risk, and it's been much more reliable now. (This has had the side benefit of making me feel accomplished early in the day, which lingers throughout the rest of the day!)