1. New Concept English Series: This is a set of classic English textbooks, suitable for beginners. It starts with basic words and grammar, and gradually improves readers' listening, speaking, reading and writing abilities.
2. Cambridge Business English Series: This is a set of English textbooks specially designed for business people, including listening, speaking, reading and writing. Suitable for people who want to improve their business English.
3. Oxford Advanced English-Chinese Learning Dictionary: This is an authoritative English-Chinese dictionary, which can help readers find new words and phrases and understand their exact meaning and usage.
4. Accelerated Oral English: This book mainly aims at oral English learning, and helps readers improve their oral expression ability through a lot of practice and dialogue.
5. English grammar encyclopedia: This book introduces various knowledge points of English grammar in detail, and provides a large number of example sentences and exercises to help readers learn English grammar systematically.
6. Official TOEFL Guide: This book is very useful if you plan to take the TOEFL test. It provides detailed exam introduction, preparation skills and simulation questions to help you prepare for TOEFL.
7. Official Guide to the GRE Test: Similarly, if you want to take the GRE test, this book is highly recommended. It provides detailed exam introduction, preparation skills and simulation questions to help you prepare for the GRE exam comprehensively.
These books are widely used and are very helpful to self-taught English learners. There are many other books to choose from, which one to choose depends on your study goals and personal preferences.