Jay Rubin is the biographer and main English translator of the works of Haruki Murakami. He also seems to relish in mocking academia, despite being an academic himself. Perhaps it's just linguistics he likes to jeer, which does make sense. I vaguely remember the silly turf wars within a university. Anyway, despite his rebellious streak, "What the Textbooks Don't Tell You" was probably just a "what THEY don't want you to know!" marketing tack-on from the publisher. It does reinforce that this is a supplementary text. Rubin seems to have been written it out of being weary of correcting his Japanese Literature students' common misunderstandings or bad practices.
Just like your English teacher in high school, Rubin is furious about the use of passive voice. He rails against the temptation to translate Japanese's "subjectless sentences" into the English passive voice. That seems to be the whole goal of the first 74 pages (the first half the book): helping you restore the "invisible subject" to translated sentences, to keep them in the active voice. Dating the book somewhat, he begins with a argument against the idea that Japanese is a mystical inscrutable language of vagueness. In 2016, it is a quaint bit of late 80's orientalism that he must have been addressing: this idea that Japan was beyond understanding. El-oh-el.
Perhaps this book was a reach for me, having been studying for less than a year. I've seen it suggested that it might be appropriate for JLTP level N3 and up. And yet, all of the Japanese here is in printed in romaji. Rubin even seems to be dismissive of kanji as a writing system at one point (waiting until page 92 to even address its absence), which is odd, but I would argue the short sentence examples are simple enough that it works better to not have to stumble over kanji or kana. The focus should be the author's message. When reviewers complain that they would find kanji easier than romaji, it comes across as an insincere humblebrag, to me. "Oh my kanji skills are so good I'd rather read kanji than sound out Japanese words in my own native writing system."
After the 70 page essay on not using passive voice, the last 1/2 of the book is a bunch of 2-page short essays on miscellaneous words and phrases. These are helpful, and enjoyable, for me to think in a new way (foreign way) about grammar, with explanations in English.
Rubin is fond of literary examples, literature being his specialty. Sometimes it seems to take him on multipage tangents, relevant to grammar lesson, but self-indulgent. Unfortunately, "Making Sense of Japanese" would function better if you could flip to a particular topic, but his writing style almost requires that you take it start-to-finish. But to achieve that, you'll need prior familiarity with a variety of grammar concepts. Hence why you might want to be at nearly JLPT N3. Although, maybe the new N4 is enough.
Since he is primarily addressing the problems of Japanese->English literature translators (and specifically that direction), rather than actual students of Japanese, he is addressing issues of nuance. These matter less for beginners understanding written Japanese and more for an editor deciding the grammatical correctness of a translation. If you do translation work, I'd definitely recommend this book. If you're more a beginner, then this book is certainly a tour of many concepts, but the most valuable parts are probably the very beginning with its useful "wa and ga" corner-cases explanation, and then the very end which teaches how to identify sentential elements in order to divide-and-conquer. Everything in the middle? Well, interesting, but a bit like a disconnected series of blog posts.