It just came out on July 1st. I am also waiting to hear from someone who benefited from this book.

Has anyone used this book, is it helpful ?

I did! - anybody can write that book in one day by just reading this forum and going through couple of chapters from Kaplan and MGMAT books. I heard great things about the Math book but Verbal book is not the best! Oh it is almost $ 50 too! But I appreciate his effort and time for putting that document together.

It is pretty much coupe of pages brief explanations of each topic and 3-4 questions with explanations. At the end of each main topic such as CR or CR there are 4-5 mixed questions.

Couple of his good advices on that document are:

+ Read the OG explanations
+ Do not spend your time on trying to learn ALL THE IDIOMS and studying hard on rare question types.

I am sure he will improve this guide in the near future.

And these advice have been iterated many times in BTG as well in Jeff Sackmann's GMATHacks blog.

I do find his articles informative though...

I personally have not seen it, but the vibe I'm getting is that you can find plenty of info on SC, CR, and RC content right here on Beat the GMAT, and with online sources such as Grockit and GMATPrep, plus of course the OG12. For practice Verbal material, MGMAT SC and Powerscore CR have a good track record. But it's also the strategies, not just the comprehensiveness of the review, so as you learn the content, make sure you're also adopting a strategic approach to each question type that is effective for you.