Life at an IIM
Reading novels helps because of its huge quantity of words. Read whatever you like and have diversity in reading like sports, science, psychology, editorials, etc., Aeon is a website where you can find lengthy articles ranging 5000 - 6000 words where you should train yourself not to get distracted during your reading process. You can read Hindu editorials, New York times, etc., Have a note book for recording the words you are not familiar with when you are reading articles and find their meaning and revise it regularly otherwise we may forget their meanings. Hope this helps.
Read Hindu newspaper paper editorials on a regular basis and try to understand also.. analyse the things which are giving you problems to understand such as harder words and take out the meaning of those words and work on it. It would improve gradually. You need to give time to yourself.. don't just
You can also go through this list once - https://www.quora.com/What-are-the-best-websites-to-read-well-written-articles/answers/16770112?ch=10&share=42297281&srid=u9NEt