I honestly don't know what to say about this book. I finished it about a week ago and I'm still at a loss for words. 
 I really enjoyed the first book. Frannie's inability to make a choice annoyed me there, but Luc stole the show for me. I really enjoyed his character and the growth he portrayed. And I found I still enjoyed him in Original sin. But not even he could save the train wreck that was this book. 
 Frannie is quite possibly the worst heroine I have ever met. She's selfish and immature and just plain stupid a lot of the time. She misses the most obvious clues and when mistakes are pointed out to her, her absolute stubbornness refuses to let her forgive and forget. I honestly hated her--worse than Nora from the Hush, Hush series, and anyone who know me knows just how deep that hatred is. 
 In all books, a main character is supposed to grow and learn. No they should not be perfect, no one is perfect, but they should at least he striving to be better. Frannie just gets worse. Her stubbornness grows, her stupidity deepens. I could not find a single redeemable quality in her. Luc--a demon--had more. 
 For someone who was tagged for heaven, she sure acted completely immoral. She was having sex with Luc constantly, then when he messed up, what was the first thing she did? Try to get Gabe to sleep with her, even though she knew the consequences of what would happen to him if he gave in (which were far worse than a regular guardian angel would get). She's just a horribly selfish, vapid girl who honestly deserves to burn in the pit. 
 In my opinion, Gabe should just let the demons have her and give Luc her place in Heaven. Lord knows he deserves it more than her.