This is a classic that I have just discovered. The book was written many years ago, but has been updated.
It focuses on non-fiction writing and has lots of great guidelines plus great advice.
My favorite piece of advice was – if you are having difficulty with re-writing a sentence, try deleting it and see what the effect is.
The basic tenet of the book is that writing is re-writing. No one gets it right first time, so be prepared for re-writing and re-writing.
I know from personal experience that I can improve existing writing – but a blank page is hard to edit.
It has specialist sections on most popular types of non-fiction writing. I skipped a few that I don’t write about e.g. Sport.
If you are interest in fiction writing check out Stephen King’s (yes THE Stephen King) classic – On Writing.