Like many other reviewers, I was introduced to this book as a student of The Open University. It is clear, concise, detailed, well-indexed, and uses a wealth of excellent examples.
Working as a technical author and teacher, I have made this a refernce text alongside Roget, Fowler and the OED. I would not be without it. From the "Presenting Information" unit of many A-Level ICT syllabii to dissertations and theses, this is an invaluable source of reference for the student.
For the author, its uses range from ideas on writing for different audiences to rather better grammatical guidance than is sometimes provided by a word processor!
For the teacher, its coverage of everything from styles of presentation to clear examples of grammar make it a book that I feel should be essentail reading as part of any route to Qualified Teacher status.
From 'Giving a talk' to 'Being interviewed for a job', it has sections that should be of use to almost anybody. To this end, I would go further than technical communication; any teacher and every post-16 student should find this book useful. Many will join me in finding it indispensable.