I admit "The Mermaid" by Christina Henry caught me by surprise, because I was expecting it to be kind of a fairy-tale retelling, whereas this was a completely original story, with practically nothing in common with the Hans Christian Andersen story "The Little Mermaid".
Still, it was thoroughly enjoyable: the clever plot, the excellent writing style, the unforgettable characters, the unpredictable twist of the ending...
My favourite quotes are:

"I don't belong to any man--not to Jack, not to Barnum, not to you. I only belong to myself. But belonging to myself doesn't mean I don't love you or that I don't want to stand beside you."

and:

"I want to be your partner, not your possession."

I think this novel should be used in schools, to teach girls and boys the difference between healthy and unhealthy relationship--it offers excellent depictions of both.
And it's also a gripping story, very well-written and with an impressive amount of research that's gone into it.
I'll definitely be re-reading it, and I'll also make sure I get a hold of the author's other novels.