This book had a lot of problems, though the biggest isn't really clear until the end.
First off, addicts aren't charming, fun, or engaging as protagonists. And that isn't fixed by letting your protagonist only act the addict when it is interesting or useful to the story. Addictions have serious consequences and in this story, it seemed like Cherry's addiction only really mattered when it was convenient to the author to manipulate Cherry into some situation she wanted her to be in.
Second, that's actually a symptom of a broader tendency by the author—many plot or story aspects only show up when the author needs them to put the character somewhere she wants that character to go. Cherry is a trained acrobat? That's useful to get her to the top of a building, but that only shows up as useful twice in the whole book. The rest of the book, Cherry is a bumbling idiot literally tripping over herself when the author wants her at a disadvantage for a bad-guy. It's embarrassingly incompetent story-craft.
Third, and this is the biggest problem (and related to the first two), Cooper manipulates circumstances to keep secrets she wants to reveal at a later time. The main bad guy is a sleazy jerk who knows Cherry in both her public and private identities. There are only two people he could possibly be (based on storycraft 101) and one of those Cooper goes out of her way to show as kind of sweet. And yet, there are moments during this book when Cherry really should have been able to see him well enough to identify him and yet (completely irrationally), she is unable to do so. At one time, she is pressed up against him with a jagged pipe pressed into the flesh of his throat, and yet the fog is somehow too dense for her to see him? He's exposed from his brow to his chin and she is literally inches away! Fog that dense isn't fog, it's soup. It certainly isn't fog that moments before allowed her to see she was in a narrow alley with bricks on either side.
Add in that Cooper pulls in the all-too-common trope of the character who cannot kill an obviously evil person when she has the chance and I lost all sympathy with Cherry, Cooper, and any future books Cooper may produce. Look, if you know somebody has killed others for kicks (because he admits as much, no less), then if you have the chance to end his depredations and you don't take it that makes you a coward and morally culpable yourself. And not just morally culpable for any future depredations he actually commits but morally culpable for all the depredations he could commit. In short, you are, at that point, committing a grossly evil act.
At the three quarters mark, I made a choice to finish the book just to see if Cooper would reveal who the bad guy was. I'm still not sure why I made it that far in the first place. By the end, I had come to regret that decision as Cooper doubles down on the stupid in every conceivable way.
A note about Steamy: There's a scene of intense and prolonged sexuality, though it is unclear (and denied) that actual sex took place. Yes, drugs were involved, but not in a condoning way. It was actually one of the more interesting parts of the book, and not for prurient reasons.