What is the main conflict in Art by Yasmina Reza?

The novel's main conflict revolves around the friendship of Marc and Serge. Conflict wreaks havic with their friendship after Serge buys a painting, and Marc doesn't have the reaction Serge expects. Over the course of the play, we learn that Marc has also become jealous of Serge's new friends, and that Serge is consumed by materialism and impressing his new friends.... belonging.