You can:
Create a rule for each value the column produces that sets the icon.
Use an advanced rule that that builds the icon name from the value the column returns. If you have icons of the same name as the values (eg. "Figlet.png"), this would be something like (untested as I don't have the column):
Code:
{:'strcat(field("book_size"), ".png")'}
Create an advanced rule using a copy of the code and change the results it produces to the icon name wanted. That would be changing "Ficlet", "Drabble" and the rest to the name of the icon.