The 'Magic Tree House' series is very good. The stories are full of adventures in different historical periods and places, and the language is simple and easy to understand for kids, which can help them learn new words and sentence structures.
One great option is 'The Hunger Games' series. It has engaging stories that can hold the reader's attention, and the language used is not overly complex but still rich enough to help with vocabulary building. The story is set in a dystopian world, which also makes it interesting for young adults.
One great option is 'The Adventures of Tom Sawyer'. It has engaging stories and relatively easy language which can help high school students expand their vocabulary and understanding of English grammar.
Another useful method is to look up new words while reading. This helps you expand your vocabulary and understand the text better. You can also make a note of these words for future review.
You can also try to look up every new word you encounter while reading at first. As your vocabulary builds up, you can gradually reduce the frequency of looking up. This helps you understand the text better and expand your vocabulary at the same time.
Taking an English speaking course with a professional teacher is a great option. The teacher can correct your mistakes and give you personalized feedback. Reading English books aloud can also enhance your speaking abilities as it helps you get used to the rhythm and flow of the language.
The 'Harry Potter' series by J.K. Rowling is also excellent. These books are full of magic and adventure, which can keep you interested while you learn English. There are many unique words related to the wizarding world that expand your vocabulary. Moreover, as the series progresses, the language becomes more complex, helping you grow with it.
Read a lot. By reading different types of English texts such as novels, articles, and essays, you can expose yourself to various writing styles and vocabulary. This helps you unconsciously absorb the correct grammar and sentence structures.
One great novel to read for improvement is 'To Kill a Mockingbird' by Harper Lee. It has rich language, complex characters, and important themes. Reading it exposes you to different writing styles and a variety of vocabulary. The story is set in a southern town in the United States, and through the eyes of Scout, a young girl, you see the racial and social injustices of the time. This helps in understanding how language can be used to convey deep meaning and different perspectives.