Book or Article, there is a difference.
As a writer, you must think about your writing project and what it will be. There is an immense difference between a book and an article. Articles are normally shorter works that cover a theme subject and several sub-themes. Word count will be one way to categorize what your project is.
Word count is not the “cast in concrete” rule. It is one of several indicators. Number of chapters and project length are other indicators. If you have three chapters or less, it is most likely an article series, not a book. It could be a book if it is three chapters plus with ten pages or more each. Another indicator is word count. If your word count is 20 thousand plus, you probably have enough for a book. Depending upon the type of book the word count can be much less if it has a lot of graphics or pictures. Do research for the genre type of your writing, and you will more specific rules for what normal word count, pages and chapters might be.
Also be careful of some other concepts. Common questions that book editors ask, some reasons that book ideas are rejected and is the core subject saleable. For some great ideas and input on what editors look for in book proposals, check out Terry Whalin’s website and articles about book proposals. Go to http://www.terrylinks.com/erbpnm. Terry has been around the publishing industry for many years and knows the business inside out.
Remember, doing your due diligence and research upfront, can save you much frustration, expense and heartache. Don’t spend three years working on your book idea just to find out that someone more famous, more experienced and “in the groove” has already done a similar work. Don’t be discouraged. Find a new way or a new twist to the material and present it. We learn from failure. Keep writing, keep researching, and keep learning!