I really believe that the best method to learn a language is to practice it. However, if you only read, you'll be good in reading and vocabulary, not in other skills. So, for me, we have to combine different ways to learn. You can read a book, but listen a radio in English, write everything in your schedule in English, try to talk to people in English too, if it's possible. It's easier if you live in a country where people speak English, but it's not impossible if you are in your own country. In this case, you have to be more diligent because you have to chase your goals. What I usually do is to study English in every free time that I have, for instance, when I go to work in the train. It helps me a lot because I don't waste my time with frivolities and I feel productive, what's good for my self esteem. Good luck! 

I wouldn't go for books with easy language, if I were in your shoes.

Hab, if you have meetings where you work, you could try to write them like un report for your boss. Or even try to report what you do, what your weakness and strenghts every work day/week/wherever fits better for you. For it, try to use more latin words because it's more formal. If you know a lot of phrasal verbs or idioms, avoid them. Look for new words in the dictionary in order to not repeat a word anyway. I have to do it in relation to each project that I submit, it's good.

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