Excellent book!
This is one of the best books on technical writing I've seen. It is composed of a set of common sense exercises that help you to cut unnecessary verbage from your writing. No deep concepts here, but just loads of practical exercises that quickly teach you remove all that blather from your writing, as well as analyze your writing for logic and flow. I bought this book years ago, back when a common proletariat could afford it, and it really turned my writing around.
I have to say, I'm a bit astonished at the price.