You can search for books within the library by going to the library's main webpage: https://library.plymouth.edu/
Once you are there, set the search to Books and type in what you are looking for. In this case, I used World War II Spies.
The initial search gave me over 300 results. If you are looking for a physical book in the library, on the left side, scroll down and check the box next to Print Book. This narrowed my searches to 71 results.
Based on these searches, it looks like many of the books on World War II Spies is within the D740-D810 call number range - which is located in the Lower Level of the Lamson Library. If you need help finding this section, feel free to ask the Reference Desk for assistance.