Two books by David Crystal who has over many years examined the evolution of the Engloish language, both in Britain and in other countries.
"The English Language" focuses on the structure, usage and history of English in three sections, over some 300 pages. "The Stories of English" is a similar book, this time some 550 pages long, but starts with the evolution of English and also has quite a bit about dialect.
Both books can be read from cover to cover or, as I have done, dipped into to answer specific questions. But they are standard works nowadays, which cover a great deal about the English language.