If you can get past the logic holes, the heroine's motivations for Returning and Jack's funky surname (because to the trite reader like me, this actually matters), this should actually be a five-star read. The lapses in logic are actually easy to overlook but what gets me everytime is Becks' reason for Returning. She's a selfish little thing isn't she? It's bad enough that she followed Cole into the Everneath after a bad case of jumping to conclusions, she has to Return to the surface to "say goodbye, properly" with full knowledge that she'll be leaving again after 6 months. That niggled on me quite a bit.I loved Cole. The ambiguity of his motivation for his actions (is he actually capable of love?) gives me something to look forward to everytime he turns up in the page. This is the complete opposite with Jack who you kinda have figured out from the beginning, and yes, even to the end. A great fraction of this book was devoted to the Cole-Nikki-Jack triangle and it was actually effective: not too cloying with enough awww- moments. Though one can argue the heartstrings could have been tugged harder, I don't think it's really what the author's aiming for.There's great allusions to Greek mythology and the story of Orpheus and Eurydice who, I must admit, I've only been refamiliarized with through Kristen Ashley's Creed (talk about out of nowhere KA mention, yes). Though not a strict requirement to enjoy this book, it could've added more depth to appreciating some of this book's nuances.Looking forward to book 2 in this series.