letters and postcards in..

[caveats]

hey guys,

I got an English(intro to fiction) exam coming up and I'm trying to prep for the essay portion of the exam. The novels we read for the class were:
The Curious Incident of the Dog in the Night Time
The No. 1 Ladies' Detective Agency
A Wild Sheep Chase
Anil's Ghost
The Lovely Bones

My prof gave us a hint that one of the essay topics will relate to letters and postcards.

So here's what I came up with so far:

In The Curious Incident, Christopher receives letters from his mother.
This showed how Christopher doesn't jump to conclusions. When he reads the first letter from his mother, he doesn't immedetialy think his mother is still alive, instead of thinks the letter was written for someone else.

In The No. 1 Ladies' Detective Agency, Mma Ramostwe gets letters from people asking for help.

In A Wild Sheep Chase, the Rat writes letters to the narrator.

In Anil's Ghost, Anil writes a letter to a director.

In The Lovely Bones, Ray Singh writes a love letter to Susie.

I have no clue what the exact topic might be. What do you guys think the topic might be? Or what are your thoguhts on the use of letters in these novels?

Thanks.