You can definitely increase the breadth of your vocabulary over time by reading constantly, and you'll probably even get a bit faster if you do it long enough. But there's a more streamlined way to become a better reader: Vocab1 and 7 Speed Reading EX. These two apps can vastly improve your abilities without sacrificing comprehension, and are now $29 when you buy them from the Boing Boing Store.
Whether you are trying to ace the GRE, SAT, or GMAT, or just become a more erudite individual, Vocab1 will help prime your brain with a database of over 520 million words. With engaging training games, you'll learn words in context, so you can actually use them correctly in your writing and conversation.
With 7 Speed Reading EX, you can drill yourself with any uploaded article or PDF, and get expert guidance through video tutorials. It comes with access to a massive library of free eBooks, so you'll have a nearly limitless amount of practice material. You can track your progress over time, and avoid bad reading habits with tailored exercises.