Fear is the Same by Carter Dickson (1956) along with the back cover copy that screams: "Many men held her body -- did any man hold her heart?" would make one think that this is a classic 1950s crime novel. Instead, it's an unusual time-travel / historical romance / murder mystery / adventure novel. While some readers of the genre might be upset about the bait and switch, I rather liked the unexpected story.
Jennifer has unexpectedly found herself living in a house in the Regency England of 1795. It is unexpected because, while she can't remember all the details, she knows she comes from far in the future (from the 1950s, in fact) and that she was fleeing some kind of danger when she was apparently sent back in time. A body must have been waiting for her because everyone knows who she is. She slowly starts piecing things together when she sees a familiar face, Phil, who she recognizes as her great love from the 1950s. Phil is also starting to realize that he has been plopped down into the past, in his case into the body of a Lord who is widely known as being a sickly wimp married to a headstrong and beautiful bitch named Chloris. As their memories slowly come back, Jennifer and Phil realize that they were lovers and that Phil had been running from a false murder charge that seemed impossible to beat. Unwittingly, they set off the same set of events in their new time zone when a murder takes place in Chloris's locked bedroom and every clue points to Phil as the murderer.
Interspersed with Jennifer and Phil's quest to prove his innocence is really quite a bit of boxing (apparently both old and new Phil have secret bare-knuckle boxing skills that they use to get out scrapes and earn money), some detailed history of the Whigs and the royal family, and some pretty great scenes where Jennifer and Phil are trying to find landmarks in a much more rural London based on their 20th century mental maps of the city. This book is occasionally more complicated than it needs to be and frequently reveals its author's delight in the details of the Regency period, but it pulls the reader along with the action sequences and has some unexpectedly great character development. I could have asked for a slightly less abrupt ending, but the book holds together well as a whole.
Carter Dickson is one of the multiple pen names of John Dickson Carr, a prolific writer of mid-century detective novels. Based on the twists and turns and energy of this one, I'd definitely take another one of his books out for a spin.