Shadows in the Moonlight

Do you remember this song?  Great song.  My favorite Canadian.  A Cool Moonlight is by one of my most favorite authors, Angela Johnson.   Sadly, I just didn't "get" this book.  Here's what I put on goodreads.com:  I love Angela Johnson so much that I feel that I need to explain such a low rating. I just didn't understand this book! I know that it had much deeper meaning than I could find. My meh feeling about it is solely "operator error" because I know that when Johnson puts pen to paper, she is magic.
Lila was born with xeroderma pigmentosum, which I really didn't know about until I read What We See at Night.  
I love Lila's family.  Her sister is wonderful and so are her parents.  And so is her best friend.  I just didn't get the friends who visited Lila at night.  I thought maybe they were angels of death or something, but they weren't.  Maybe I will read this again someday and figure it out.  I'd love for someone to read it and explain it to me, because I know that it is meaningful, I am just to dull to understand it!