If you've ever hovered over a comma or a hyphenated word, wondering if you've written it correctly, you may be interested in Fit to Print, by Janet Hughes and Derek Wallace.
This is a 2010 revision of the former New Zealand Government Style Book. The book clearly explains correct use of punctuation, capitalisation, use of numbers and referencing. There are plenty of examples to illustrate each point. While you may not read it from beginning to end, it's written in an engaging style, and you'll definitely feel in safe hands whenever you refer to it.