learn it! title
Can reading significantly improve grammar and vocabulary?
story books
Mr Lim from Malaysia asks:

I have started to read story books to improve my English. But the problem is I cannot read them fast or understand them well. The few authors I have read are John Grisham, Jeffrey Archer, Sidney Sheldon. I just fell in love with the books but am unable to finish them fast. Do you think I can improve my vocabulary and grammar if I read a lot? My grammar is very poor.
If your preferred strategy for improving your English is reading, then read on! Reading is a great activity and is one to be enjoyed. You don't need any additional resources: just yourself and a good book.

I see you have a preference for adventure stories and crime fiction novels, or thrillers which are many people's favourites, including mine. The authors you have chosen all write exciting stories, ones designed to grip your attention as you read on towards the final solution. But the plot structure is quite complicated at times, there are often many different characters, the syntax is sometimes complex and the vocabulary load quite heavy. And these three authors tend to write very long novels. I see that 'The Runaway Jury' by John Grisham is 400 pages long and 'Kane and Abel' by Jeffrey Archer weighs in at 550 pages!
So, if you want to read adult fiction written primarily for readers with English as their mother tongue, the advice is: choose stories that will grip your attention, ones where the plot structure is fairly straightforward, ones with not too many characters, ones with relatively easy-to-understand syntax and vocabulary. And ones that are not too long! Then you will stand a good chance of finishing them!
But don't just choose adult fiction of the above variety. Try some of the ELT reader series too. Original stories written by ELT writers with exciting plots and good characterisation where the grammar and vocabulary has been kept relatively simple so that you can read on and finish the story in an afternoon or over a couple of days. Adventure and crime are favourite genres in these series too.
Macmillan Heinemann, OUP, CUP and Longman Penguin all have exciting series. In the CUP series, try levels 4, 5 or 6 (top level). The ones that I know personally with an adventure or crime theme are: 'Death in the Dojo' by Sue Leather; 'Dolphin Music' by Antoinette Moses; 'Trumpet Voluntary' by Jeremy Harmer; 'He knows too much' by Alan Maley and 'When summer comes' by Helen Naylor. I can guarantee that you won't be able to put them down once you have picked them up!
And, yes, I do think that your grammar and vocabulary will improve if you read a lot. If you are reading a story that you enjoy, it is likely that you will re-read sections that you are particularly attracted to and the vocabulary and syntax in these sections will be more memorable and usable. All the CUP series are recorded on cassettes too, if you want to work on your listening skills, and they all come with worksheets if you want to work further on comprehension and language extension activities.