Who is Marketa from The Book of Laughter and Forgetting and what is their importance?

Marketa is Karel's wife, she has an affair with one of her husband's mistresses, Eva. She invites Karel's mother to visit them after the mother loses her husband, even though Marketa and Karel's mother do not get along very well. Her analysis and relationship with Karel is a statement on love and how actions in a couple's collective past set the stage for their present and future actions. During Eva's stay, both Karel and Marketa decide they are tired of operating in the same old way because of trivial actions they made in the past in their relationship.