Into everywhere - Paul J. McAuley

The Jackaroo, those enigmatic aliens who claim to have come to help, gave humanity access to worlds littered with ruins and scraps of technology left by long-dead client races. But although people have found new uses for alien technology, that technology may have found its own uses for people.

The dissolute scion of a powerful merchant family, and a woman living
in seclusion with only her dog and her demons for company, have become infected by a copies of a powerful chunk of alien code.

Driven to discover what it wants from them, they become
caught up in a conflict between a policeman allied to the Jackaroo and the laminated brain of a scientific wizard, and a mystery that spans light years and centuries. Humanity is about to discover why the Jackaroo came to help us, and how that help is shaping the end of human history.