After first finding out about Zen JiuJitsu, I hesitated for a few days before buying it, or even downloading the free sample. Frankly, I've blown a lot of money on supplemental materials for BJJ that are all collecting dust on a bookshelf or drawer somewhere. Finally I ended up reading through the sample. When I came to the end of it, I clicked the "buy now" link without pausing. From only reading the sample, I figured out three things:
1) The author doesn't just give lists of techniques to learn. It is more of a discussion about our mindset and strategy for approaching training. "Philosophy" if you will. In the age of the Interent, finding random techniques to practice is a piece of cake. What we need to figure out is how to choose the techniques we NEED.
2) The author's writing echoed my own thinking about BJJ and learning in general.
3) It clearly represented a fresh perspective.
I've been learning BJJ for a few years now and have spent big money on various DVD sets and books, and hours upon hours watching YouTube videos. The vast majority of these books, even the 'bibles' of the BJJ world seem to focus exclusively on cramming as many techniques as possible into your head (although they may differ on WHICH techniques or the finer points of certain ones).
The problem is, I have never learned well this way. Trying to learn German and Spanish at various points in my life by studying flashcards for hours on end proved to be as fruitless as it was tedious. And yet, now I am nearly fluent in Korean, one of the hardest languages in the world for native English speakers to learn. I've done it through directed, systematic, study and a LOT of immersion. And I've had fun doing it.
Zen JiuJitsu advocates a similar approach with learning BJJ. You may not go to the gym every day of the week, but the book provides you with a study plan (and the ability to customize it) to make the most of the days you can't make it in. He shows you how to use this time systematically (regardless of your level and individual strengths/weaknesses) so you're not whittling it away on YouTube pointlessly trying to memorise details of random techniques. As such, you won't have to join any additional gyms or buy extra equipment. You'll create a custom study plan that you'll need to spend a little bit of time (he recommends an hour) with every day. That's it, just a little a day. That's how you can really make progress towards reaching the threshold of 10,000 hours of practice required to achieve mastery.
I really think that anyone, at any level of the game, any fitness level, and any age can benefit from the methods recommended in the book. It doesn't just prescribe a certain progression. Rather, it teaches you to look at your own skills, create your own improvement plan, and, finally, implement it to see serious leaps in your game.