There were many possible answers to this question, depending on one's personal circumstances and preferences. If you're used to shopping online and like to look up information about various products online and compare them, buying self-study materials online may be a good choice. You can buy textbooks through online bookstores or self-study stores. These stores usually provide a variety of textbooks, tutorial materials, and other learning resources. You can choose the appropriate materials according to your needs. In addition, you can learn more through online courses and video tutorial. On the other hand, if you prefer to go to the bookstore to buy teaching materials in person, you can better understand the contents and versions of various teaching materials, and you can also communicate with other students to obtain a better learning experience. Buying self-study materials online or going to the bookstore in person is a good choice, depending on personal circumstances and preferences.