The title of this book, Bad Language, correctly indicates that it is about language use (especially of English), which is, or is considered by some to be, in some sense bad. If you pick it up in the hope of reading yet another rant about the decline of standards, you will be disappointed. On the contrary, Lars-Gunnar Anderson and Peter Trudgill, who are professional linguists, state in the Introduction: "It is our hope that, after reading this book, at least some people will not be as harsh in their linguistic judgements as they have been.". But also, they aim to help people recognise situations where certain language forms are inappropriate or inadvisable, and so keep out of trouble, while encouraging them to deploy their full expressive range in appropriate circumstances.

The kind of bad language discussed is mostly vocabulary. Non-standard verb forms feature to some extent (e.g. done for did), including non-standard negation (e.g. ain't and double negatives), and there is a chapter which discusses grammatical matters such as clause-final prepositions. The first and last couple of chapters are rather general and the chapters in the middle more specific, covering swearing, slang, filler words, the grammatical proficiency of native speakers, accent, and language change.

The book is written in a clear, easily understood style using rather short sentences with rather little nesting of clauses. Here is a sample paragraph:
"The creative aspect of slang is important. The point of slang words is often to be startling, amusing or shocking. Something must be done to make them stand out against the other, more ordinary lexical items."
but this is perhaps more typical:
"When speakers use slang words, they are often aware that they are doing so. When we speak, we concentrate on finding the right strategy for presenting the content we want to communicate. Words with primarily grammatical function come without effort — only foreigners worry about a, an, the and words like that. The important thing for the native speaker is to find the right words which will give precisely the intended meaning. Slang words, however, can be important for finding precision in expression, rather than in content."

I must admit that I found it rather difficult to stick to reading this book. Partly, I think, the style is in parts just too simple for my tastes, but more important is that most of the material was already familiar to me and I largely share the authors' views, so I am not really part of the intended audience. Certainly there are plenty of people who might benefit from reading such a book rather than, for example, rereading Strunk and White.