Reading in a second language is a great way to improve your vocabulary, books are good but you should try to read magazines and newspaper too, they have several advantages over books.
Reading many short articles is far better than just one long book. There will be many topics and new words
if an article isn't interesting you can move on to another newspapers and magazines have many sections. Sunday Newspapers are some of the most varied with many supplements a Sunday newspaper could last all month.
You can find interesting information when you read in English and learn what is culturally important to British people. Information is one main reason we read in any language.