EDIT: I did finish Kiss of Steel, and I HIGHLY recommend reading these books in order. The majority of my questions were answered, and I have a better understanding of what was going on. 
 Tarnished Knight is labeled as book 1.5 in Bec McMaster's London Steampunk series, and I think reading Kiss of Steel first might be beneficial. I can't say that for 100% sure, since I haven't read it yet. There is little to no world building in this story, and there seems to be an assumption that the reader knows who/what the Bluebloods (I think a different type of Vampire) and where/what the Rookey is, along with some familiarity with the characters. So I am going to keep recommending that these books be read in order. One fairly important thing I need to point out is that steampunk really isn't that prevalent. Don't mistake me, there are mentions of artificial limbs and some other odd technical things in the background, but that's about all. Which worked for me, since I am new to the idea and understanding of steampunk. 
 John, aka Rip, is a newly made (6 months) vampire. He is trying struggling to get over his bloodlust while investigating a murder and the disappearance of one of the street women. Things escalate from there, and in the middle of the action you have the UST between him and Esme. he is a big man, and ashamed of his artificial arm, thinking it makes him even less human than he already is. 
 Esme is Blade's (Rip's boss?) housekeeper. Who happens to be completely head-over-heels in love with Rip. Not that she tells him, or that he notices. Which is the main conflict in this book. I almost think the Slasher plot should be considered secondary to their love/hate/love relationship. Esme wants to be his thrall, he doesn't want to risk tasting her and loosing control. (view spoiler)[When Esme stumbles across him feeding from one of the street women, they have a falling out. (hide spoiler)] 
 Dancing around the subject, and each other, makes up a chunk of the story. Their sex is another chunk, and the Slasher storyline is basically a filler to lead up to the end (view spoiler)[result of Rip FINALLY feeding from Esme (hide spoiler)]. 
 Quick read that was a free offering, this is only about 3-3.5 stars. I have recommended this to a friend that likes steampunk, but I won't be egging her on to read it, nor will I recommend it to anyone else.