This book found its way into my reading pile because it was recommended by the instructor in my creative writing course.
It's a straightforward and comprehensive guide to writing better English. Graham King has sections on grammar, punctuation, spelling, a guide to difficult and confusable words, expanding your vocabulary, how to improve your writing, foreign words and phrases, and abbreviations and acronyms.
On these topics, it is the book I've found easiest to understand, and my writing has improved as a result.
I recommend it to everyone who wants to write better, whether you're a writer or someone who takes the language seriously.