These two self-published grammar training books are a passion project from Akuzawa Noboru, a Japanese salaryman who struggled with English until he developed his own study method. Now he's put his method in book form so you can use it to learn Japanese.
At its core, his strategy is simple: treat Japanese grammar and sentences like a formula, put the formula in your head, and solidify it through repetition. You can achieve this through what Akuzawa calls the "Sentence Pattern Method" and the "Read Aloud Method." This requires you to create a batch of Japanese sentences for your target grammar and repeat them aloud with self-checks fifteen times a day for four days.
With such a straightforward approach, what makes these books worthwhile? The author has done all the prep work for you. Grammar points are separated by JLPT level, N5 and N4, and five sentences per grammar point are written out in English and Japanese. All you have to do is pick up the book and study.
There are drawbacks, though. The books lack the polish of a professional editor, and the price is just slightly too high to make it an easy purchase. There is romaji, but thankfully it's separated into romaji-only lists that are easily ignored.
Japanese Sentence Patterns will be a benefit for some and not others. If you're struggling with grammar after studying a Japanese textbook and need a mountain of example sentences and repetition to get these patterns solidified in your brain, this might be a viable solution. (And adding the sentences in these books to an SRS might be an even better solution.)