The most challenging part is the back and forth between centuries and if you are not familiar with French history then that will make it more difficult to follow. Other than that I loved it. I want to read his other books now. 

Better than the TV adaptation. Right away you get to see the main characters develop. you get a feel of Cornwall and its challenges and before you know, you are part of the village like a good neighbor who sees everything but says nothing. 

The story is really good and fun but there’s one big flaw for me. Some paragraphs are really repetitive — same action, same character struggle but with different synonyms. It’s unfortunate because you feel at times that you are reading what you just read so it drags the story unnecessarily. Except for that the story is really good. 

When it comes to Stephen King, I am biased. I really enjoyed going on a fantasy adventure. The world he created was fun and I enjoyed the good vs evil dynamic. 
I have difficulty not to love one or more of his characters. 
Charlie is not your typical teenager but it is not a typical story either. His companion is a sweet dog Radar. Together they make a sweet team. I believe Stephen King wished he could put Molly his dog on the quadrant from his story where Charlie put Radar. Any dog lover would. 

I am very biased with Stephen King. I love Holly the book and character. I discovered her in Mr. Mercedes, which I adored. Holly surprised me in this book — especially towards the end but she was believable.  Extreme situations can make people do surprising things and she did.