A few other SF books with the idea of an external co-brain: - Psychohistorical Crisis by Donald Kingsbury (plays a major role) - Accelerando by Charlie Stross

A few other SF books with the idea of an external co-brain: - Psychohistorical Crisis by Donald Kingsbury (plays a major role) - Accelerando by Charlie Stross (minor role) - The Peace War, Marooned in Realtime by Vernor Vinge (relatively major roles) edited for formatting