I think this one was missing a little of the Mayberry magic for me. Don't get me wrong, it is still a superbly written book with a great emotional tug. However I think the book took so much time dealing with both Mike and Angie getting over and grappling with their feelings of loss for Billie that I thought the romance element suffered a bit for it.
To do the story justice, the time and attention to the healing process was necessary. Also, SM always does a great job of moving a relationship from the platonic to the non-platonic sphere. She just has a knack. It never feels awkward.
But as I said, I wanted more time with just the two of them feeling what they feel for themselves without Billie's presence (or absence) hovering over it.