This book is amazing. It helped me a lot during exams. This is must buy product for 9th grade students. I felt like teacher is teaching while reading this book(but no book can replace teacher). I suggest you to buy. But the cover of book is poor(not so much) and they will become dog eared books(I used this book for 6 months and I handle them with care). I bought all the science books for 9th grade. They are also very helpful.