grab a half dozen novels, any novels - maybe 2 fat ones, 2 skinny ones, 2 normal "pocket book" ones. Count the number of words that fit across a page on random pages, maybe 3 per book, multiply that by how many lines there are on a page. Take the average words-per-page times number of pages for each of your books. Add up the numbers, and divide by 6. That is, if you really want to know. Otherwise, like someone else says, guess between 80,000 to 120,000 - that sounds pretty reasonable.