I also have a book called "the explorer STAMP ALBUM" let's just say I was trying figure out what's missing out of it, it's jus easier to say it's missing 175 stamps total out of it.
With all due respect, most collections have stamps that are mis-identified and placed in the wrong spaces. Most of us have done it. Some intentionally and some because of lack of knowledge. So all of those spaces that are filled need to be rechecked for accuracy. As others have said, assume that you have the most common stamp and go from there. Good luck in your search.