Book collecting is a hobby, that once started, can easily get out of hand! You probably have several favorite books, and perhaps you'd like to have a first edition. Some book collectors get hooked by buying a book at a yard sale, and realizing that book they paid a quarter for is worth a hundred dollars! It happens all the time, the key is knowing what you are looking for.
One person can't be an expert on every book, but a good place to look for value is in finding the early editions. My interest started with Charlie and the Chocolate Factory, by Roald Dahl. First editions (1964) can fetch thousands of dollars. Early editions (still in 1964) can easily fetch $100 if they are in good shape.
You may have some classic valuable books. Here's a search engine that can help you find the value of your book treasure.