Man does this author know how to spin a tale. I really enjoyed this one. I didn't find it particularly "dark" It was twisted for sure, but more in "Dateline Episode" sort of way.
It was well written, and kept me guessing straight through to the end. I do think it could have been a bit shorter. After the big climax, I thought it dragged a bit. The characters were complex and well written. Although, I was a bit angry and turned off by one character's reaction in the aftermath of her situation. I didn't understand it AT ALL, and it made me sort of feel less sorry for her plight. There is also a secondary romance type thing going on with one of the characters that seemed out of place for me. I didn't think it was needed, and it did distract from the main plot for me because enough time wasn't invested in this couple to make me believe this "insta-love".
There is romance in this, but "I" personally didn't feel it was a "romance" book. More along the lines of an erotic psychological thriller. Rest assured though, there is a HEA for 99% of the characters in the book
Overall though, a very worthy book from this author.