Adventures in Japanese is aimed at junior high and high school learners and as such, the material is not as comprehensive as you might find in other textbooks.
That's not necessarily a bad thing. The simple "this = this" explanations enable you to dive into using and understanding Japanese right away.
A unique feature of AIJ not found in other books is the lesson review at the end of each chapter. You're given grammar exercises that test your knowledge on key concepts from the chapter and a checklist of things you "can do" with your new knowledge. If you're not passing the review quiz or can't check off an item on the checklist, you know exactly what you need to study before moving on. This is a great barometer for progress and a great selling point for this series.