At first, I was a bit annoyed because no progress really happened regarding Justin's disappearance and fate until the book almost ended. But after I thought about it, this book isn't about Justin anyway. It is about Adam and Ethan. The missing Justin sure contributes to their story but not everything must be about him.
Overall, I thought it was pretty engaging. It sure kept my attention until the last page. I liked that RJ Scott took time with Adam's memory, and not making it easily returned just because he met Ethan. There was quite a long journey for Adam to get there, even if he was reassured with Ethan's feeling for him along the way.
I was a little miffed with the resolution between Ethan and his father, Marcus, though. It happened off page, between the last chapter and the epilogue, and I felt like I was robbed a very significant moment.
PS: I haven't read the first book but I totally had no problems following the story