Over the years I've come across lots of books that have helped me tremendously in my writing, even though they don't appear to have anything to do with business.
Here are some that live within arm's reach of my desk because I dip into them all the time.
Mars and Venus in the Workplace by John Grey
It's primarily about relationships between the sexes and how they operate in a work environment. But before you run for the hills, it's also a great education on how men and women think, speak and respond differently. Really useful when crafting your message and how to present it.
How to Get Ideas by Jack Foster.
If you're ever stuck knowing what to write, grab this book, wander over to your favorite coffee shop, and do some of the exercises. It shows you how to come up with more ideas, faster and easier. It teaches you how to become "idea-prone" and takes you through a five-step procedure for digging up creative ideas. Lots of quirky illustrations too.
The Analogy Book of Related Words by Selma Glasser
It's not a dictionary of synonyms. It covers a series of topics such as acting, aeronautics, money, sales, insurance, travel and many more. Under each topic is a list of words and phrases that could be related to the topic. Some you wouldn't think of. For example, under the topic "love and marriage", you'll find everything from "aisle" to "old maid" and phrases such as "eternal triangle," "justice of the peace," and "mating season." It'll certainly broaden your thinking.
Woe is I by Patricia T. O'Connor
A plain English guide to writing plain English. It's a grammar classic updated to include the Internet age. From the jacket blurb: "common-sense, jargon free, even witty answers to all your questions about the basics and subtleties of grammar, style and usage." It's fun, charming and useful whether you have to write or speak for your business.
Eats, Shoots and Leaves by Lynne Truss
I never thought punctuation could be funny but leave it up to Lynne Truss to find the humor in periods and semi-colons. This is a spirited and playful look at the foibles of the colon, comma, ellipsis, dash, and other signs; how to use them properly and the effect you create when you do so. Worth reading for entertainment value alone.