It's a novel by Alice Kuipers about a daughter and mom how they communicate with each other by leaving notes on the refrigerator everyday.
I think this is exactly how human relationship has turn out recently, rather than having real conversation, people email, sms, msn to each other. There is nothing wrong with it and in fact most people are more encouraged to communicate through writing than talking, however, lacking of the warmth of voice responding might lead to certain misunderstanding. Sometimes it's still nice to do it in the old-fashioned, manual way, just talk to each other.
