Devlin is the faerie High Court assassin. He has only ever disobeyed his queen once: when he spared the life of a halfling named Ani. Now Ani is all grown up, and Devlin likes what he sees. Boom chicka wow-wow!
I have to be honest here and say I really didn't like Radiant Shadows. At all. Actually, I couldn't even finish it--I got about halfway through and decided life was too short to waste on this book.
My main problem with Radiant Shadows is that it seems like a novella artificially stretched out into a novel. There simply is not enough material here for a full novel. The conversations run in pointless circles that lead nowhere, and events and information are very repetitive. How many times do I need to be told Ani's been threatened and is completely capable of killing? Or that Devlin saved her life? Once is enough, thanks.
In addition, there are a lot of continuity issues, and things happen randomly with no explanation. In one scene, Ani asks her brother to make dessert, then calls Irial to tell him she's making dinner. Then she asks him to come over a protect her from Bananach and immediately packs a bag and leaves the house. Um, wut? I have no idea what Rae, Devlin's dead mortal friend who can walk in people's dreams, has to do with anything in this story, or why she's in this novel; and ditto with Ani's steed, which just appears with no explanation. You're not going to wonder where that came from, Ani?
The strength of Melissa Marr's novels are that she takes the tropes of a typical YA romance and really thinks about how they would apply to her characters, twisting the story in unexpected ways--that's what I loved about both Wicked Lovely (review here) and Ink Exchange (review here). I didn't get any sense of characters or thought in Radiant Shadows, though. It felt like Marr was making the novel up as she went along.
To me Radiant Shadows was nothing but filler in between Fragile Eternity (review here) and Darkest Mercy. Not that anything I say is going to stop a fan of the series from reading it--nor should it, since you probably don't want to be lost when you start the final book in the series--but personally I was pretty disappointed.