Clear Light of Day does contain a frame story structure. The novel starts with the characters in adulthood, and then flashes back to show past events; at the end of the book, the narrative returns to their present. The central portions of the novel serve as backstory and new information for both the characters and the reader.
This narrative style serves to interest the reader in the past life of each character, showing the result first, and then the cause; the last section of the book, which wraps up the various plotlines, serves to "frame" the story in the present. Everything has already happened, so the adult characters make a deliberate choice to continue on with their new knowledge.