Aw, that’s easy-peasy. You just count the number of words on an average text-only page from the book in question, multiply that by the number of pages in the book, then subtract from that the number of non-text pages in the book and multiply the result by pi and then divide that by your age on your last acknowledged birthday and…. Oh, heck, you’re a writer and I’m an editor, let’s skip the math and just use this shortcut: go to renlearn.com and click on their “Quiz Store” tab. Type in the book title, press GO, then click on the title in the search results and viola! Word count.
FYI, I’m not affiliated with Renaissance Learning. This lovely feature has been known and referenced by curious writers for years.