Phil and I have self published 2 books of his poetry. We call our little publishing co. The Dishes can Wait Publishing. Phil's been a book scout, a rare book dealer & collector most of his life. From 1999 - 2004 we had an online rare book business and from that experience I learned how to identify and value rare books. Phil and I have taken on the task of valuing several privately owned libraries for insurance purposes. Here I will share the basic criteria that we use to value a book.
#1 Condition. One of the problems a bookseller faces in pricing books by using the internet is the fact that they have to rely on someone elses interpretation of what Fine, Near Fine, Very Good, Good and Fair are. For the critera that we use to classify condition I refer you to the Independant Online Booksellers Assciation.
#2 Compair like books available with the book you have - How many are listed that are like the one you have in edition & condition.
#3 Determine the fair market value based on the availablitiy, condition, and demand.