Not actually a novel, but a short story. Available on Tor.com, this is a great story about love, regret, and mermaids.
I'm always cautious with mermaid stories. Like a lot of fairy tale creatures, they're easy to do too rosy-sparkly or too melodramatic dark. This story seems to catch the middle ground, a mermaid who is enticing, enigmatic, and exotic, but still strange and divorced from humans. She is other without losing her appeal, which keeps us sympathetic to the narrator of the story.
Interested in reading Monstrous Beauty, a novel set in the same world with some of the same characters that will be released in early September. We'll see if a whole novel holds up to this story.