This short little book looks at some common (and not so common) British words and phrases. It's arranged roughly by theme with words associated with that particular theme (food, people, language, manners and mannerisms, etc.). The explanations are relatively short (a paragraph or a bit more) and moving onto the next entry.
That's basically it. It's perhaps more helpful if you've not as familiar with some of the words/phrases and might make a good gift for someone who is going on a trip to the region/studying abroad, or someone who has a particular interest in language/linguistics. It isn't exactly groundbreaking though and you can find other books of a similar nature (I think 'Stuff That Brits Like' is very similar to this in format).
Not much more to say. I bought it cheap and am glad I did so. Otherwise I'd recommend the library but I wouldn't rush out to read it either.