I just received a children's book for my son.  The book looked to be in really good condition.  I was flipping through the pages and in the back there are word cards (like flash cards to be cut out).  Some of these cards have been cut out.  Is this OK?  I am really not sure and don't want to make an issue out of it if it is not against the rules.  I can say that it is the first thing my son noticed and was very disapointed.

I'd say that it wasn't postable because it is missing key things that make the book whole

I would say that it is probably unpostable or the sender should have sent you a pm to confirm if you would still want it with this missing first.

The question that makes it unpostable or postable is this: Can the book be read without the flash cards? Is it still complete without them. If the book cannot be used without the flashcards..ie  "now find the card with the word CAT" then it is unpostable. If the cards were additional bonus then it is postable. What is the ISBN number of the book?

Here is what the Help Center says;

• Books that require non-Media supplementary materials MAY NOT be posted

  • an example would be a book that requires a decoder or craft materials

• Books that originally had accompanying non-Media materials that are not required to read the book MAY be posted.
  • The extra material does not have to be included, and if it is included, the book must not be sent using Media mail rate.

If the cards are reqired then you need to politely contact the sender and request your credit back. If the cards are not required, you and your son could make flashcards together, to go with the book.