I have written two articles on this topic and this will be the last.
In the previous article, I say that beginners are recommended to be able to read English from the grammatical point of view before they start extensive reading. In this article, I will discuss one more recommendation for beginners in English.
The second thing you should do is to study a grammar book and keep learning grammar rules. I don't think I have to argue for the importance of grammar for comprehension of English. So here I would like to argue for the importance of studying a grammar book. It is useful in some ways. First, it gives you explanations of grammar rules in a systematic way. This system is important in that it helps you learn a new grammar rule more easily. Suppose you want to learn the difference between "almost" and "most." If you know the system of grammar, you can easily understand the former as an adverb and the latter as a determiner or as a pronoun. This distinction will, in turn, prevent you from saying things like, "Almost the students passed the exam." Second, it provides you with multiple example sentences. Suppose you have difficulty in understanding what is notoriously called a "concatenated relative clause." Then try looking it up in a grammar book and it will give you several example sentences as well as the grammatical explanation. By studying them, you will get used to this grammatical structure, so that you will never find yourself confused by it again. Thus, by studying a grammar book, you will be able to read more and more books with sound comprehension.
In conclusion, I would like to repeat, emphatically, that I don't recommend extensive reading to beginners in English. It is advisable for them to study the grammatical system and learn to read English grammatically in advance. And when they have done these two things, they are no longer beginners in English. But, if you are a beginner and really, really, want to start extensive reading, you should follow these two rules: (a) Select reading materials written in English plain enough for you to understand it grammatically. (b) Make sure that you understand them grammatically time and time again by consulting your teacher.
Thanks for reading.