Wherever ONCE BITTEN TWICE SHY is shelved (I picked it up in the sci-fi/fantasy section), don't be deceived: it's really chick-lit. And the worst kind of chick-lit, where there's a whole lot of "defining the relationship" and not a lot of action or romance. The book starts six months after protagonist Jaz is partnered with vampire assassin Vayl, and their relationship is already completely unprofessional. We miss out on all the fun, getting-to-know-you, tension-building parts of their relationship and pick up when they start to trudge glumly through the Swamp of Complicated Emotions. Rardin tries to convince us that Vayl is an uber-alpha male, but he spends so much time talking about his feelings it's really hard to buy. He also lets Jaz push him around a lot...and not in that "I'm humoring her" sort of alpha-male way, more in a "I'm totally whipped" sort of way.
The fact that one of villains the duo have to face is Vayl's late wife (she's a vampire too) means that even when Jaz and Vayl head out to kick some ass, they always end up right back at that Swamp of Complicated Emotions. The super-villain plot is drenched in Eau de Catfight.
The urban fantasy/paranormal elements are poorly realized and confusing. The growth of Jaz's "Gifts" is pretty botched - each new development is greeted with less explanation than the last. I never got a clear handle on what it meant to be a vampire in Rardin's alternate reality. And Rardin was trying to do a techno-mystical fusion with her uber-villain plot, something to do with a cult of demon-worshippers and a biological WMD (these basic elements are revealed early on), but devoted very little time or effort to explaining either.
The other main plot point is the slow reveal of Jaz's tortured past to the reader. We are informed a number of times that there is a HUGE TRAUMA in Jaz's past, and then we start to get hints about what it is, and eventually we learn the whole story. This just made me think, again, that this book starts after all the real action is over. I was also kind of annoyed by the way that the story came out - she blabs the whole thing in pieces to totally random people, and actually seems over-eager to talk about it, but when she's not in chatter mode she goes on about how her HUGE TRAUMA is too huge and traumatic to talk about, or even think about. It's exactly the kind of drama queen behavior that makes you wonder how this girl ever got a job in the CIA.