Time Thief by Lind Buckley-Archer

The Time Thief : Being the Second Part of The Gideon Trilogy

Kate made it back to her time, but Peter is stuck in 1763. However, Kate did not return alone!  The Tar Man, a villainous eighteenth-century criminal, returns with Kate to twenty-first-century London.

Time travel makes this science fiction genre.  But part of the story is in 1763 London with real historical characters, so it is also a little bit of historical fiction!