LEFT TO TELL: Discovering God Amidst the Rwandan Holocaust; by Immaculée Ilibagiza, with Steve Erwin; Hay House, 2006; 215 pp; hardcover, $24.95.

If you want a book with the emotional impact of an earthquake, you must read “Left to Tell.” It is the gut-wrenching story of Immaculée Ilibagiza, a Catholic woman in Rwanda, whose reliance on prayer, specifically the rosary, saved her life and her sanity.

In 1994, Ilibagiza, then 22, spent three months hiding in a bathroom to avoid the bloodbath of the Rwandan massacre, which led to the extermination of one million people.

But a warning: This story is not for the faint of heart and certainly not for younger readers.

Ilibagiza, a Tutsi, grew up unaware of differences between herself and friends who were Hutus and never gave tribal matters a second thought. She was born into a loving Catholic family and was deeply cherished by her parents and brothers.

“It was paradise,” she says of her early years, when she lived happily with her hard-working parents and three brothers.

When the bloodbath against the Tutsis was suddenly unleashed, her father’s last loving gesture was to give her his well-worn rosary beads, which she kept with her throughout her ordeal.

Separated from her family, she sought refuge in the bathroom of a pastor’s home, where she experienced a spiritual transformation. As the months wore on, she and the seven other women in the small room had to remain silent to avoid detection by the killers. Unable to bathe, they were tormented by lice, and suffered agonizing muscle cramps from lack of exercise.

Tortured by hunger and anxiety, Ilibagiza had visions, and she never doubted they came from God. In one, Christ told her that she would lose her family but would always be his daughter.

When others succumbed to despair in the hot, stifling confines of the bathroom, she read the Bible and prayed the rosary constantly. And when the devil assailed her with doubts, telling her that God had abandoned her and she would surely die, she just prayed harder.

Astonishingly, as the killers circled the house, carrying spears and machetes and calling out her name, she tried to do something that many other Christians might never have considered. “I tried to pray for them myself, but it felt like I was praying for the devil.”

When Ilibagiza finally emerged from the bathroom, weighing 65 pounds, she discovered that her life as she had known it was over.

Her parents and two of her brothers, along with many other relatives and friends, had met grisly and horrendous deaths. The family home had been burned to the ground, and everything was stolen.

The turning point comes when she meets, face to face, the man who was responsible for killing her family in cold blood. Everyone expects her to spit on this man and curse him.

Instead, as he cringes before her, a broken-down prisoner of the people he had tried to eradicate, Ilibagiza begins to weep.

“He had let the devil enter his heart,” she writes. “And the evil had ruined his life like a cancer in his soul. He was now the victim of his victims, destined to live in torment and regret.” She then does the only thing that seems possible to her. She tells him, “I forgive you.”

Fortunately, the story has a happy ending for this woman who followed Christ.

Today, she lives in New York City with her Catholic husband and two children. She devotes her time to a foundation that she created to help the many children in Rwanda who were orphaned in the massacre.