Isn't the library's catalog available online? Most are. But you could try this... https://www.loc.gov/rr/program/bib/libsci/faq.html#class1 . How do I find a book's Dewey Decimal Classification (DDC) number or Dewey call number? There is no comprehensive resource or database that you can check to locate a book's Dewey Decimal Classification (DDC) number or Dewey call number. The best place to begin your search is the Library of Congress Online Catalog. When you open a record for a book in the catalog, look for a field labeled "Dewey Class No." If this field is listed, it will give the book's DDC number, as below: ... or the OCLC world catalog... http://www.worldcat.org
The library website says they don't have the book, but I want to buy it anyway so I have it for a long time. The library links to a website to search libraries in the area that does not let you search by ISBN or DDC. I looked at the DDC from OCLC and noted numbers to look at. A few months ago I was at a library when a women was looking to read about finding a job. I looked at the DDC list the library had and I did not see a category that included finding jobs.