The Water's Lovely by Ruth Rendell

Twentysomething sisters Ismay and Heather Sealand live in the bottom flat of their childhood home, while their ill mother and aunt live on the top floor. When they were teenagers, their stepfather, Guy, drowned in the family's bathtub. Ismay has always felt that Heather killed him to protect Ismay from his advances. Ismay has never confronted Heather about her belief but grows concerned when Heather has her first serious adult relationship with Edmund. Should she warn Edmund about her suspicions? Meanwhile, Edmund has his own family issues--mainly, his clingy hypochondriac mother, Irene, who doesn't like Heather. Also featured in the book are sister and brother Marion and Fowler Melville. Marion looks for older people to exploit, hoping that they'll leave her money in their wills. Fowler spends his time living on the streets. Slowly, the Melville siblings' lives intersect with the Sealand clan's to form a story of psychological suspense. I loved The Water's Lovely and could not put it down. While it's not fast-paced, Rendell creates such interesting characters and situations that you don't want to stop reading. You want to find out where the story is going to go. As good as her recent books, Thirteen Steps Down and A Sight for Sore Eyes, despite a few coincidences in the story.