So, you want to learn English or at least learn it better. Even if you don't, there is sure to be someone -- a teacher, a spouse, a child, a boss -- who thinks your life, your career prospects or even just your vacation options would be greatly enhanced if you did. No problem there, you think; Japan is chock-a-block with English-language instructors. So it is, but as any language student knows, and a book published in America last month confirms, the process may not be that simple. Before you can learn English, it helps to know what English is, and not even native speakers can agree on that.

In "Do You Speak American?" -- the companion to a television documentary and sequel to the hugely popular "Story of English" (1986) -- authors Robert MacNeil and William Cran share findings from a cross-country trip they took to determine the state of "American English" today -- in effect, to find out whether there is, or ever was, such a thing. Some academics and language purists, the authors write, seem to believe that there once was, but that it is now in sad decline. Others argue that American English has always been a hodge-podge of regional and class-specific dialects, but worry that those might be vanishing under the pressure of cultural homogenization.

Unsurprisingly, Mr. MacNeil and Mr. Cran discovered that there is no simple response to either of these concerns. They did discover that quirky, regional English is flourishing across America, even though everyone in the country watches the same television programs, eats the same fast food and buys the same name-brand clothes.