Overall, the similarities outweigh the differences. The core emotions and themes in the 'a sign of affection' manga and anime are the same. However, the anime might add some extra visual effects or change the sequence of events slightly to make it more engaging.
I'm not sure specifically as there could be many novels with this title or related concept. It might be about different ways people show affection in a fictional story, perhaps romantic love, friendship love or family love shown through the characters' actions and relationships.