Is there a way I can find out the value of a possibly "rare" book?

It is available on Amazon as a paperback for $20, but for a real price contact a local rare and old book store. They will want to look and touch the book.

These people are asking $59.99 for a copy on eBay. It’s about halfway down the page in the left column and if you click on the image it will take you to their auction posting.

What your book is worth depends a lot on its condition and, like most things, whether there is a market for it. They only way you can be sure is to either do as @Tropical_Willie suggests and take it to a rare/antique bookseller and have them take a look at it or see if you can find a bookseller online who will appraise from a description or from images.

I have some books that may be rare too. The reference I got, but which I have not yet looked into is: Bookfinder.com Try it.

It won’t be worth what you might think. Books are not valued as highly as they should be in my opinion.

Take it to a rare book store.

For what it’s worth:

The last time I tried to sell an antique book online, my source informed me that only rare booksellers are allowed to sell antique books. I had to physically take it to a book seller and offer it to them.

http://www.rarebookbuyer.com/webuyoldbooks/ or start on their portfolio page for more information.

Perhaps you might try getting some appraisals? I can’t vouch for this company, but it will at least give you an idea where to start. They state that they give free estimates and offers for books of interest to them – using pictures and info about the book that you also email them. I was just using this site for reference. I also found this site in New York City that deals with old and rare books – http://nycrarebookdealer.com/. I wish you the best of luck on your adventure!