It has quite a few unnecessary things and the theory is not well organized. As a result, you get lost and the situation usually doesn't become easier as you would expect from a guide. Also, this leads to it being around 1,000 pages, which doesn't make it user-friendly for transportation. Some things are not explained further. I was not satisfied overall, even if it is recommended as the best

Very good book. It was recommended to us by our best man who is a math teacher for my daughter.
It has well-written basic theory elements, to the extent needed for the student to understand the problem-solving method.
It has plenty of examples per category, and then many exercises for the student to practice.
This is how we do it: After the child solves the school exercises for each chapter, we find the corresponding ones in the extracurricular book, we go through the examples together, and then we have them solve some exercises.
If we see them struggling with a certain category, we help them understand the solving method and then have them solve all the related exercises in the book within the next 7 days. This way, they improve.
This method works perfectly fine.

The mathematics textbook for 1st grade of middle school is excellent and can be used comfortably by both parents and students. Its specialized knowledge provides the corresponding validity.