Sister, by Rosamund Lupton

At last, an excellent mystery--well-written, interestingly structured, scary, and yet moving.

The book is written as a letter to younger, flightier, sometimes annoying sister Tess (who we quickly learn is dead), from older, more settled sister Bee. Bee is recounting what happened from the time she learned that her sister was missing and boarded a flight from New York to London through the unraveling of the mystery of Tess's death. The police rule Tess a suicide, but Bee is sure that she would not have killed herself even though she was grieving the death of her newborn son. As girls, Bee and Tess lived through their brother's death from cystic fibrosis, and Bee knows that this experience gave Tess an appreciation for life that would have made suicide unthinkable. Because Bee did not know that Tess had already had the baby, however, the police discount her claims that they were close and thus reject any insight into Tess that she might offer.

Because the police won't investigate, Bee begins digging into her sister's life, and there is much to be discovered--the married professor who fathered her child, the obsessed photography student who was stalking her, the pregnant Polish friend with the abusive boyfriend, the experimental genetic engineering treatment administered to her baby prenatally to cure cystic fibrosis, the money Tess suddenly had to spend on an expensive layette. Bee buzzes from suspecting one person to another as her own life falls apart--she is fired from her job, breaks up with her boyfriend, and seems to be ill.

As she investigates and grieves, Bee learns not only what happened to Tess and why, but gains insight into how she, her sister, and their mother dealt with the losses of their childhood. Through it all, Bee returns to her love for Tess to sustain her, even when she must face how sorely she failed the younger woman.

Favorite passage:

I used to think "stillborn" sounded peaceful. Still waters. Be still my beating heart. Still, small voice of calm. Now I think it's desperate in its lack of life, a cruel euphemism packing nails around the fact it's trying to cloak.