Extensive reading in English with the help of a good English dictionary on a variety of real life topics is one of the ways to learn English vocabulary. Since there is an enormous amount of reading material in English, a learner of English has to prioritise reading in subjects according to learner's needs for using English to encompass first the most necessary, relevant and frequently used vocabulary. Day-to-day topics ought to come first in reading.
Reading materials can be arranged by level of difficulty of vocabulary - for learners at beginning, intermediate and advanced levels.
Learners can master the most important English vocabulary by reading thematic texts (materials), first of all on everyday topics with important content, for example : Practical Tips and Advice to Make Everyday Life Easier and Better (practical solutions for everyday problems). Such self-help books on settling everyday matters are available at book stores.
In addition to thematic informative texts (materials), learners can read thematic dialogues (samples of real life conversations between people), narrative realistic stories, fine literature, newspapers, magazines, Internet materials, books in various subjects, general thematic English dictionaries, etc.
Good general thematic English dictionaries arrange vocabulary by subject matter (topics) and provide clear word usage explanations and also a few usage sentences for each word meaning which is especially important. English synonym dictionaries provide usage explanations and usage examples for words with similar meaning. Thematic general English dictionaries combined with English synonym dictionaries are a valuable tool for mastering English vocabulary logically, comprehensively and intensively for real life needs of learners.
Good public libraries have a wide selection of English reading materials.
It is better for learners to write down unknown vocabulary in whole sentences to remember word meanings easier. It would be a good speaking practice for learners telling the content of the texts that they have read. Learners can write key words and phrases or main ideas as a plan or questions on the text that require long answers to make easier for learners to tell the content of the text. I believe it is a good idea to read each logical chunk or paragraph of a text and to narrate each paragraph separately and then the whole text. As people say, practice makes perfect.