About Eleanor of Aquitaine, set in the high middle ages. It's a bit more 'naughty' than the norm for these books (a few times I have hoped that other people on the train aren't reading over my shoulder!) but while it seemed a bit like a Mills and Boon initially I now see the relevance as a way to illustrate the marked decline in her marriage to Henry Plantagenet.
And am enjoying reading about someone I had known nothing about, while I realise historical novels are 'enhanced' I do think they make history more digestible and Alison Weir is a noted historian who writes factual books as well as novels.
According to my Kindle I'm 47% of the way through and following a quick Wikipedia search I have lots to look forward to!