I'm not quite sure where to begin on this one, so as I think of things, I'll mention them. 
 First, I'm not fond of the voice used to tell the story. That was part of my issue from the start, so it probably felt like it dragged more in part because of the voice. I was more okay with it by the end, but only because I'd become used to it, not because I liked it. Some praise the 'painting pictures with words' aspect of it; I thought it was too much. It often (especially in the beginning) felt like we were given detail for the sake of detail and not necessarily useful information to the story. I felt like I was sifting through mud to try to find the actual nuggets of plot or characterization. 
 And wow, did this book drag in the beginning. By 25% into the book, I wasn't sure that I was going to be able to finish it because it felt entirely like backstory and we hadn't gotten to any of the meat yet to really hook us. I put the book down for a while because it didn't interest me in continuing. By 50% in, we were still just barely beginning to get to the main part of the story. Still drug a lot at this point, though not quite as badly. The last 20-25% of the book made it worth buying and reading, and is honestly why it received 4 stars instead of 3. 
 This one shared some of the same repetitiveness issues that BOatK had, though there was more point to them this time. I still thought there was trimming to be done, particularly with some of the flashbacks and dreams which felt unnecessary. I despise flashbacks in the middle of action sequences for the sake of 'slowing things down' too. I'm always tempted to skip that and go straight for what I want to know about and not what the author wants to tell me about. I just got so tired hearing about how much Benji was still grieving and how unfair it all was and how much he loved his father and his father loved him. I got the point during the first half of the book. 
 Though I found the call-out (it's not really a reference, just an in-joke for those who recognize it) to BOatK rather cheesy, the interweaving of the events from Burn into the fabric of this universe is quite well done, reminiscent of CLAMP cross-overs in their Tsubasa: RESERVoir CHRoNiCLE, Volume 01 and xxxHolic, Vol. 1 series. Please note this is from someone who has not yet read Burn - I still recognized enough to know it was being referenced in this story. It does make me curious to find out what they're talking about, but I've heard Burn's ending is a bit enfuriating, so I'll likely wait for the next in that series to come out first. (Plus I'm wondering if these mentions are spoilerish or not as far as a certain angel turned 'god' is concerned.) 
 I loved Nina. 
 The end of this story, however, is very emotionally charged, and as I said, quite worth the reading of the rest of the story. Once I got there, I enjoyed the ending immensely. Yes, there were tears. 
 So, if you can make it through the beginning and don't mind the myriad flashbacks to how much Benji is grieving for his father, then this story might be for you. If you've lost someone of your own, be prepared to drown in Benji's grief because it will hurt you. I highly suspect the first time I lose someone that close to me, I'll need to re-read this.