Can a crocheted bookmark be included with a book at the media mail rate?  Or would I need to pay the first class rate?

No, you should not include anything in a Media Mail package other than the book and the 2nd page of the PBS wrapper.

Ok, thanks!

My postal clerks allow book marks, but this interpretation varies widely across the country. . . therefore, you take a chance when enclosing extras.

I've had found bookmarks, postcards, business cards in some  of the books that I've recieved, maybe included accidently or maybe not.  But they're 'paper' so not sure about a crocheted bookmark

Anything incidental and directly related to the Media Mail item can be included so bookmarks are supposed to be fine as long as they are not advertising. I've received a few without a problem. But, the enforcement of media mail is messed up, so I wouldn't risk sending a bookmark unless it would be vitually invisible when tucked inside the book.