The good thing about learning to write well is that every books is a book about writing - or at least every good book.

Increase the number of top quality books that you read and your language will naturally improve. It's not a magic recipe, and it won't happen overnight, but it will happen.

One way to make sure that what you read is always good is to focus on the classics - Dickens, Twain and so on - and also the (good) translations of foreign classics - Dostoievsky, Hesse, Marques... those are usually very well written and translated, and the more you read of them, the better your written (and spoken) english will be. Try reading one book every week or two or thereabouts.

Between that and constant practice (with feedback where possible), you should see your writing skills go from ok to good and eventually excellent within a matter of years.