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This book largely covers material already addressed in more popular books (like O'Reilly's Mind Hacks & Mind Performance Hacks and Thinking Fast & Slow), and while it covers that material in a breezy and readable style, such a style is not really well-suited to the content: it's somewhere between the theory-heavy Thinking Fast & Slow and the abstract list of mostly-independent tips and exercises of the O'Reilly books, yet reads like a budget version of Oliver Sacks. The O'Reilly format is much better suited to the content, which leans heavily toward tips and exercises, and had the author adopted that style (and moved the background material to section introductions) the result would be a book that's significantly easier to go back and reference.

It introduces just a handful of ideas not already widely covered in this genre. They have their own chapters, but are easily summarized:
Exercises that develop balance, proprioception, and manual dexterity (such as tai chi, games involving throwing balls, and model building) are useful because they build up networks for embodied thinking while also giving us a way to release some physical energy while engaging the default mode network.
Waking life can be divided into four mood states: calm energy, tense energy, calm tiredness, and tense tiredness. Tense tiredness is unpleasant -- a state of irritability and low productivity, and should be minimized by going to sleep. Calm energy and tense energy are both useful for productive work (calm energy being, basically, a flow state, and tense energy being the kind of productive-yet-edgy state that caffeine ideally induces) and calm tiredness is useful for daydreaming. Switching from calm tiredness to calm energy can be done via light exercise, such as a brisk walk. A nap converts tense tiredness into calm tiredness.
Visualization exercises can improve not just visualization but also observation.
Creative rearrangement of reminders of emotionally potent past events can be useful for improving autobiographical memory.

Furthermore, he covers a couple things that aren't usually in these books but are in adjacent parts of the general self-help genre: the basics of CBT and DBT, pranayama, simple meditation. He borrows ideas about journaling and notetaking from productivity books (which often overlap with this kind of book), while he otherwise mostly focuses on improvement of actual brain function.

Basically, if you've read Mind Performance Hacks and Thinking Fast & Slow and then read (and understood) the previous paragraphs, there isn't much point in actually picking up this book: it's very short and contains very little new information. On the other hand, it's also inexpensive and a quick read (it could be conceivably read in a single afternoon, though I didn't), so if this kind of book is your bag it's better than most of the genre.

My most serious criticism is a habit this shares with other popular science books written in a breezy style: the author summarizes popular yet clearly flawed arguments credulously or makes arguments that contain big leaps in reasoning (either because the arguments are flawed or because the material that fills in the gaps was cut for being too technical). Specifically:
The author credulously repeats the idea that modern media causes ADHD (and that reading books on a backlit screen is more likely to cause ADHD than reading books on a page) without going into any more detail about his reasoning than the obviously-flawed and sloppy op-eds that make the same argument do. Maybe he has an actual argument and just didn't include it, or maybe he has never bothered to really consider the argument he's repeating. Either way, repeating this sloppy argument casts doubt on whether or not he should be writing a book about how to be more intelligent!
The author repeats the idea that listening to Mozart makes you smarter, again without really explaining his reasoning (other than to say that music builds up networks for recognizing patterns). The study he cites was extremely weak, and has since had many criticisms and failed replications. He doesn't cover this, even though the criticisms appeared basically immediately. If he read the study itself rather than media coverage of it, then not mentioning the obvious criticisms in this book is unforgivable.
* He claims that listening to music you like is better for brain development than listening to music you don't like. His argument is that different networks light up. He doesn't elaborate on what these different networks are. So, his conclusion doesn't follow from his argument, and his argument is trivial (after all, different networks light up when you look at a red ball vs a blue ball, but that doesn't make one better than the other, nor does it indicate which is better). There are plenty of good reasons to believe that listening to music you don't like is better for brain development (since, after all, mere exposure is enough to engender positive feelings with regard to music up to a certain point, so music you don't like is usually music whose components you are unfamiliar with: explicitly seeking out uncomfortable music is a way to broaden your horizons, something he suggests doing with books!)