This book is one of the most depraved dark romances I've ever read, and I would advise you to read the TWs very carefully. There are some scenes in here that could definitely trigger someone who went in unprepared. That said, it also has a really unique premise and ends up being a really fascinating psychological portrait into two deeply traumatized individuals, while also providing some brilliant dialogue on consent, and I ended up liking it a LOT more than I thought I would!
The two main characters are Aurora, a college dropout working as a truck stop prostitute, and Tobin/Kane/Jax, a trucker with a dark past who has some side deals with some shady people. When he sees Aurora, he wants her... but he's not what he seems. This is basically a Why Choose but all the men are actually the same person, because the leading man has DID (dissociative identity disorder).
Dissociative identity disorder is one of the most interesting and controversial psychological disorders, even amongst professionals. My Forensic Psychology professor didn't believe there was sufficient evidence for it to be real (I remember her arguing with a student about it during one of her lectures), but my Abnormal Psychology professor found it credible, at least following an episode of extreme trauma. It's also been called multiple personality disorder or split personality (and people often confuse it with schizophrenia), but now it's categorized under the dissociative disorder umbrella.
I thought Lauren Biel did a really great job with the research she clearly did for this book. I also like how even though this book had some pretty gnarly scenes of sadistic sex and degradation (he penetrates her with the business end of a knife and has her suck on a public toilet handle, for example), Aurora had agency. It was limited agency and she did what she did because she felt like she didn't have a choice, but it was different enough that she didn't categorize it with the trauma she had from another incident in her life. I thought the choice to make both Aurora and Kane's trauma happen off-page was very sensitive, and I also felt like it made sense why the characters did the things that they did. This relationship is by no means aspirational or desirable, but it worked for them. I'll admit, I wasn't sure how she could possibly write an HEA for these two, but she found a way.