English is spoken by a significant proportion of the world's population. How did one language become so dominant and how does the English spoken in one place differ from that spoken in another? If you're interested in such questions then you might like to take a look at The Story of English
by Robert McCrum ,Robert MacNeil and William Cran
The book isn't so much about the roots of English - there are a couple of chapters on its early history - as a celebration of the diversity of the English language. The authors look at Scotch and Irish English, at the differences between American and British English, at Cockney, Strine (Australian English) and many other versions of the language. The book ends with a look at the future of English. I felt that the concentration on diversity was a weakness in the book - the authors give much less prominence to factors which promote uniformity in language. For instance the internet gets pretty much no mention, despite the third edition of the book being published in 2002. Certainly it's a highly informative book, and if you've watched the TV series on which the book is based (which I haven't) then I can see this as a useful resource for taking the subject further. However, if you're looking for a history of the language, or a discussion of diversity versus uniformity, the I would suggest that you look elsewhere.