I liked about 2/3 of Fathomless. Unfortunately, once the plot twists of the final 1/3 of the book were revealed, the whole thing was pretty much ruined for me. 
 It's too bad, because there's a lot to like about Fathomless. It seemed from the outset like a sensitive, interesting take on the classic Little Mermaid story. Life under the sea is not filled with singing crabs and dolphins, but rather with a bunch of mermaid lost girls, former humans who were brought by an "angel" to live in the ocean, where day by day they forget their former lives and identities. But when one of these girls encounters a human girl on the shore, she starts to remember who she was... and to realize that the angel story might not be the truth. 
 But, but, but... the plots just goes off the rails, and a completely out-of-place element is introduced, and the book falls apart. I was engaging in some serious eye-rolling by that point, and maybe even a little unladylike snorting as well. 
 If you want to know the cause of my eye-rolls and snorts, you can read my spoiler-filled review here. 
 Suffice it to say, my overall reaction to this book is: No. The lovely descriptions and interesting set-up do not justify the mess that is the conclusion and resolution. Nope.