So I had a look through the preview of this textbook and I think if you’re using it as part of a language school class it should be fine; you can supplement it with some of the free online resources. Why do I think that?
- in the class you’ll hopefully get extra explanation and examples from the teacher, beyond what’s in the book
- at the N3 level it’s good to start getting used to explanations of Japanese grammar in Japanese
- many N3 and up grammar points are just simpler and less in need of long explanations
- when you find something confusing, doing a web search for “だろう grammar” or whatever will bring up multiple resources, so you can find the one that seems clearest
The shinkanzen books also tend to be quite short on explanation.
If you want books with grammar explanations in English, my personal recommendations:
- The Dictionary of Basic Japanese Grammar, and its Intermediate and Advanced sequel volumes. These are the most detailed and comprehensive I know of; they don’t cover every possible “grammar point” but they get the important ones and what they do cover gets a lot of coverage per point, which I think is a good tradeoff. There’s a forum book club that went through Basic last year and is about to start Intermediate.
- A Handbook of Japanese Grammar Patterns for Teachers and Learners, aka 日本語文型辞典 (link is to the Tofugu review). I actually have the original Japanese-only version of this, but I am assuming the coverage is similar; the review has screenshots. This isn’t as in depth as the DoBJG etc, but it has wider coverage, so I tended to use it as my secondary reference. You could alternatively just use web resources like bunpro instead of this one. Also available in Korean, Thai, Vietnamese, Chinese and Japanese versions.
So it depends on your budget – I really do recommend the Dictionary series, especially if you like a paper reference book, but if money is tight then you’ll be fine with the textbook and free online resources. If you have a Japanese book buying habit like me you can supplement with 日本語文型辞典.