This book tells the history of the English language, and I have to say, before I started reading I was a little concerned that it would be boring; it seemed like a very academic book and I worried that it wouldn't really be very engaging. I've read things like this before which were very informative, but written in a very dry, boring style.
The good news about The English Language is that it is very entertaining to read; I think this is a very important quality for non-fiction works, as the information is much more likely to stick with you if you enjoyed yourself while reading it.
When reading, you'll gain a general overview of the language's entire history. You'll learn about the other languages which fed into it, the origins of phrases, etymologies of words and lots more. One bit I remember being particularly entertaining (and enlightening) was a comparison of the same passage from the Bible as presented in the different translations.
So if you've ever wanted to gain a stronger understanding of how languages develop and what roots the English language has, The English Language is definitely worth a read. It's not enormously long, so it obviously doesn't go into a huge amount of detail (think of it more of an overview) but it is still very interesting and informative. I definitely recommend it.