The Milky Way is conscious. Thirteen billion years old, spanning four hundred billion stars, thinking in timescales that make civilizations look like sparks. It has a plan. Humanity is part of it. They just don't know that yet. Collision with Andromeda spans seventeen million years and follows the Okonkwo family across the full arc of that plan and everything that follows from it. Scientists who build weapons they don't fully understand. A woman who becomes the galaxy's living interface. A man who spends four centuries answering a wrong that was done to his family. Generations who scatter across the stars carrying names that mean more than they know. Above them all, the galaxy watches. Patient. Hungry. Telling itself that what it is doing is necessary. It is wrong about that. The consequences are larger than it imagined. The novel works at two scales simultaneously. Its galaxy POV chapters render non-human consciousness with genuine alienness, no pronouns, no human grammar, a mind that measures time in stellar rotations and cannot quite perceive anything as small as a person. Its human chapters are grounded in grief, stubbornness, and the persistence of identity across millennia. Readers of Iain M. Banks and Arthur C. Clarke will find the scale familiar. The moral territory is harder to place. Collision with Andromeda does not resolve into lessons. It resolves into consequences, and it makes you feel the full weight of them. A seventeen-million-year story about what it costs to mean well, and what it costs when meaning well is not enough.