The Quiet at the End of the World by Lauren James

Lowrie and Shen are the youngest people on the planet after a virus caused global infertility. Closeted in a pocket of London and doted upon by a small, ageing community, the pair spend their days mudlarking for artefacts from history and looking for treasure in their once-opulent mansion. Their idyllic life is torn apart when a secret is uncovered that threatens not only their family but humanity’s entire existence. Lowrie and Shen face an impossible choice: in the quiet at the end of the world, they must decide who to save and who to sacrifice.