Walking to Babylon by Kate Orman
This was the very first Bernice Summerfield novel I read, long long ago, and then a few years back I then really enjoyed the Big Finish audio adaptation guest-starring Elisabeth Sladen as a Babylonian priestess. I realise now that it's also partly a homage to Iain M. Banks: the story is about a far-future civilisation, the People (a pretty direct copy of the Culture), two of whom take it into their heads to go to ancient Babylon, with potentially catastrophic results. An archeologist from 1901 gets swept up into Benny's mission with unexpected consequences. I really enjoyed it when I read it effectively as a standalone novel back in 2002, and I enjoyed it even more now.