Can you tell me the monetary value of my books?

We do not provide financial appraisals of books or manuscripts, but there are many antiquarian booksellers who do. A good place to find an appraiser (if you live in United States) is the American Booksellers Association of America (ABAA). You can search their Directory of Booksellers by location or specialization.  

The Rare Books and Manuscripts Section (RBMS) of the Association of College and Research Libraries also has an online guide to assessing the value of rare books entitled Your Old Books.