The two basic reference books for writers are the dictionary and the thesaurus. There are several good ones available--both in hard copy and online. However, if you want to find the exact word you need for a particular subject or build your vocabulary, whether the subject is technology, geography, history, architecture, business, politics, history, and so on, there are two books you should definitely own. These are THE ULTIMATE VISUAL DICTIONARY published by DK, and WORD MENU published by Random House.
THE ULTIMATE VISUAL DICTIONARY provides you with excellent graphics, cutaways, and illustrations of objects ranging from the Hubble Telescope to the violin, and labels each part of the object. For example, did you know a modern drum set that a rock band uses has at least three cymbals: the ride cymbal, the crash cymbal, and the hi-hat cymbal? You can learn what they are, what they look like, and what they do. Do you know what the frontal notch, supraorbital notch, and supraorbital margin are? Well, you might want to or need to if you're studying biology, nursing, and medicine.The Visual Dictionary provides you with clear illustrations and graphics so you can develop visual learning skills.
The WORD MENU provides another great writing resource. Categorized by sections that focus on technology, the economy, psychology, or medicine, you can discover that elusive word for something you can't quite describe. Want to know the name of a particular wrench? The book lists 35 types of wrenches and explains what each one is used for. Have you wondered why the income tax code is confusing and complicated? The Word Menu lists over 200 terms used on income tax forms and explains what each terms signifies.