Book — Alastair Reynolds

Three hundred years in the future, Verity Auger is a specialist in the archaeological exploration of Earth, rendered uninhabitable after the technological catastrophe known as the Nanocaust. After a field-trip goes badly wrong, Verity is forced to redeem herself by participating in a dangerous mission, for which her expertise in invaluable.
Using a back door into an unstable alien transit system, Auger's faction has discovered something astonishing at the far end of a wormhole: mid twentieth-century Earth, preserved like a fly in amber. Is it a window into the past, a simulation, or something else entirely?