I loved the ambiguity, the way that the novel can be taken at face value or seen in the light of a game with no rules, indeed a game to the death. The sisters both love and hate each other; Cassandra is a private person who resents and is cruel to her sister; Julia is always trying to gain Cassandra's attention without any respect for her privacy. They part company after involvement with a young neighbour, Simon, but are later re-united on their father's death.
Julia attempts to become part of Cassandra's life again, and in doing so gains material for her latest novel. She then publishes the novel, almost a biographical work of Cassandra and her relationship with Simon, the ultimate betrayal of Cassandra's need for privacy. Cassandra finds the intrusion unbearable and commits suicide.
A review cannot do justice to the intensity of feeling that Byatt inspires. There are some passages which are too detailed, and the portrayal of Cassandra's insanity, Simon's fascination with snakes, also some of the Quaker background, become boring at times. However it is worth skipping through those parts to get the full enjoyment out of this excellent novel.