This just wasn't for me. I haven't read the other Night Huntress books featuring Cat (this was my first NH book, got it for cheap at the grocery store), so First Drop of Crimson wasn't exactly convincing me to read any of the other books. 
 The plot is lacking. There's a demon who is after Denise's entire family because hundreds of years ago, one of her ancestors screwed over said demon and now he wants REVENGE. This revenge is somewhat halted because he makes a deal with Denise to let her find Nathanial, her ancestor. Unfortunately most of the book consists of Denise and Spade meandering around aimlessly, basically acting like they'll get luck and run into Nathanial. But then again, of course the plot is practically non-existent so more important things can be focused on, like Spade and Denise's blazing sexual tension and love! /sarcasm 
 Denise is a pathetic heroine. The first half of the book she walks around with a stick lodged firmly up her posterior, immersing herself in the supernatural world but hating every minute of it. She hates vampires because they killed her husband. I don't exactly know what happened (not having read the other books) but it sounds like one of those "a small group of people did something bad so ALL people like that are bad" situations. The second half, when she gives in to her RAGING LIBIDO that flares up around Spade, all she can do is internally moan about how she isn't good enough for Spade and throws herself pity parties. Finally, she pulls the old "I have to do everything even though I am PHYSICALLY and MENTALLY INCAPABLE of doing them because I don't want my friends to get hurt" bullshit and randomly takes off to face Raum, the demon, alone. There's nothing redeeming about Denise, in my opinion. She seems like some weak, poorly contrived character who happened to be convenient for Spade to lust over. 
 Speaking of Spade, I liked his character a lot better, up to a point. He seems like one of those male characters that starts off pretty awesome in a series, but then gets put into a relationship and becomes a pussified, lame shadow of his former self because of TWU WUV (biggest offender being Adrian Ivashkov from Richelle Mead's Vampire Academy and Bloodlines series. And no, I will never let that go). Spade seemed pretty badass up until all his mushy thoughts and actions towards Denise and how he would do ANYTHING to be with her, then I lost what little interest I had left. 
 (view spoiler)[The book ends with Denise staying as some shape-shifter demon thing thanks to Raum's marks (because self-sacrifice FTW) and her and Spade get married. Gag. (hide spoiler)] 
 I think I'll be skipping the Night Huntress series.