McFadden books remind of episodes of procedural TV or mystery/thrillers you put on to turn your brain off. The writing is not spectacular but good enough that it doesn't pull you out of the story. They are quick reads and decently paced. The predictable template of set up, plot twist, second plot twist, teetering resolution is easy to digest and gets the job of a thriller done. 

The Coworker, of course, follows this same structure. I enjoyed the plot twists but wished for a more satisfactory ending - found the

Murder of Tara by Natalie to be interesting but wished there was some sort of comeuppance for Natalie, that she didn't just get away with everything I think I would have found the ending much more satisfactory if we waited a bit longer for the reveal of Dawn being alive and behind the whole thing and ended with Natalie in jail

Overall, good but not my favourite of McFadden's works.