Back in the day, the way that people figured out how many words were in a published book was to count the number of words in a few lines on a page, divide by the number of lines, and then multiply by the number of words on the page. If you wanted to be more accurate, then you counted the number of words on a couple of whole pages, divide the total number of words by the number of pages you counted, and then multiply by the number of pages in the book.
However, these days, you can find out how many pages are in a published book much more easily. Here are a couple of possible sites that will tell you how many words are in a published book:
Renaissance Learning Click on “Quiz Store.” Type in the book title, press GO, and click on the title in the search results.
Or, try http://www.perma-bound.com/library/ Enter the book title in the search box, click on the correct book, and then click on Reading Information. This provides lots of good information, including Reading Level.