This book suffers from a mild case of Second Book Syndrome. The first act hasn't got much of a plot beyond "everyone tries not to die while they process the ramifications of what happened in book one." When the plot does show up, it's remarkably similar to Angelfall's plot:
Penryn searches for her little sister and ends up at a fancy dress party in an angel aerie right before all hell breaks loose.
There are, of course, some big differences, like the glimpses into Raffe's past and angel politics, and there's also an uptick in the amount of tragi-romantic mooning, unfortunately. Teenage me would have probably gotten all tingly at the thought of an Adonis-like angel and a teenage girl falling into forbidden love. Adult me can't get past the ick factor of the millennia-wide age gap. And yet the entertainment factor is above average, despite a samey vibe to it that's a bit disappointing.
I still like Penryn and Raffe (though he's hardly in it except for flashbacks), Pooky Bear rocks my socks, and Paige is turning into quite an interesting character aside from her propensity to go missing. However . . . If Penryn has to go after her sister in book three, I'm declaring this author a one-trick pony. It's an entertaining, very readable trick, but still.
In other news, in a cosmic fluke or strange twist of fate, Susan Ee totally predicted the 2016 US Presidential Primaries: Uriel/Trump is set to go head-to-head with Michael/Clinton after everyone ensured Raphael/Sanders was screwed out of his party nomination. Spooky, no? :P