Just guessing but I feel like what he meant was that she wouldn't notice it was the books she ordered and not the she wouldn't notice they were books under the cloth. If it's not that the yeah it's pretty stupid.
@Chibi-Angi I think the idea was that if he covers them up before she gets close she won't be able to see the titles or authors and thus wouldn't be able to figure out what books they were. As for the cloth, I guess it would give him a reason to admonish her if she attempted to remove the cloth herself without permission and he'd obviously wouldn't give it willingly.
@WhatAnOrigianalPlotSaidNobody I like to think her mother was going into labour and then she was like "nah I'm not waiting" and just clawed her way out alien style, killing her mother.