[mothered]

Both the DNA and empty box methods are appropriate.

If the book Is very light weight, you can probably get away with boxing them without using dry Ice and the like.

Not if I have to go pick it up at the post office in person. Then I won't be able to say It didn't arrive because I'd have to sign for it.

Who's to say It was "you" who signed for It?

After It's been picked up, go to the post office and request to pick It up and then express your disappointment when they tell you It's not there. Human error Is Inevitable, hence administrative errors and/or lack of cross-checking Identifiable Information happen all the time.