Japanese the Manga Way isn't a "textbook" in the traditional sense; it's more of a fun supplement. But it's a very useful, fun supplement.
In 493 lessons, the book introduces bite-size grammar explanations with accompanying examples from real manga.
The explanations are accessible and the manga reinforces the target concepts. You shouldn't make this your primary study resource, but instead use it to get alternate explanations for grammar points you're learning in a more formal textbook.
For more, read our full review.