The worth of any old book depends upon supply and demand. How many copies were originally printed? How many are still around today? How many people are interested in paying for and owning a copy now? And yes: what condition is your copy in? One way to get a sense of these answers is to search for the title and author on the online aggregate search site, http://used.addall.com. Here you can see what copies of the book are being sold by dealers of used books around the world. Be sure to type the name of the publisher in the keyword field. You can narrow down your search by filtering out editions that don’t seem to match yours, through the boxes at the bottom of the search results page. Even if your book is listed by other dealers for good amounts of money, you would still need to find someone who would be willing to buy it. Good luck!