Throughout her life, Elizabeth Lesser has sought understanding about what it means to be true to oneself and at the same time truly connected to the ones we love. But when her sister Maggie needs a bone marrow transplant to save her life, and Lesser learns that she is the perfect match, she faces a far more immediate and complex question about what it really means to love—honestly, generously, and authentically.

Hoping to give Maggie the best chance possible for a successful transplant, the sisters dig deep into the marrow of their relationship to clear a path to unconditional acceptance. They leave the bone marrow transplant up to the doctors but take on what Lesser calls a “soul marrow transplant,” examining their family history, having difficult conversations, upending old assumptions, and offering forgiveness, until all that is left is love for each other’s true selves. Their process—before, during, and after the transplant—encourages them to take risks of authenticity in other aspects of their lives.

But Maggie’s body does not ultimately prevail in the fight against relentless illness. As she and Lesser prepare for the inevitable, they grow ever closer, their shared blood cells becoming a symbol of their enduring bond. Told with suspense and humor, Marrow is joyous and heartbreaking, incandescent and profound, revealing how even the most difficult experiences can offer unexpected spiritual growth.