There's a lot of the paranormal in this historical romance - the hero, the Earl of Rockhurst, is one of a line of special humans known as the Paratus whose job is to fight against evil creatures which periodically are able to slide into this world through a 'gate'. This Paratus has his assistant, a wolfhound Rowan, but knows the risks of getting involved with a woman who could be used against him by the evil creatures.
Unfortunately Rockhurst finds himself involved with a rather unusual woman - unusual in that she's invisible. He doesn't know the identity of the woman he names Shadow but she saves his life and he wants to find out more about her, especially when he realises her invisibility is caused by a very special ring, one which, if he obtained it, could mean he could once-and-for-all banish the evil creatures against which he battles.
But Shadow, otherwise known as Lady Hermione Marlowe, doesn't want to reveal her true identity to Rockhurst, a man she has loved for years. She has met him lots of times and he's ignored her - she's not beautiful or interesting enough to tempt him. After making a wish she finds herself invisible between dusk and dawn and so sets out to learn more about Rockhurst, becoming dragged into his battle against the evil creatures at the same time. What Hermione doesn't know is that Rockhurst may have to kill her to get the ring, and that other people are also after the special magical ring.
I did enjoy reading this book, particularly its spirited heroine Hermione. Rockhurst, too, was an interesting and tortured hero although I felt his dog stole a few of his scenes. As a paranormal the occasional lapse of historical accuracy didn't seem to matter as much (people's dialogue slipped into American rather than British English several times). Hermione's fears that Rockhurst wouldn't be interested in her if he actually saw her were well written and I also liked some of the side characters. All in all this was a good read.