There's a difference between a series of books (many of the same characters, different stories) and a serial -- a book that's published in chapters. This book had so many unresolved plot lines at the end that it was like reading a chapter in a magazine where you have to wait until next month to find out what happens next. That widespread lack of resolution in the plot lines kept me from giving this book four stars.
Additionally, I thought the pace was a bit slow -- you could have edited 30-40 pages out easily, and should have. Too much time is spent describing characters' brooding thoughts -- and there's a lot of brooding in this book -- when thoughts are best expressed by actions and, to a lesser extent, dialogue.
One plot line involves an Amish family, in which Grace is the central character. There's a secret in the family that's making Grace's mother very unhappy -- so unhappy that she takes to wandering around the countryside at night. Her unhappiness is bothering everyone in the family. Grace is being courted by a young man, so there's a plot line involving that, as well.
Another plot line involves Heather, a non-Amish young woman (an Englischer) who comes to stay as a boarder with an Amish family for the summer. It's never clear how she got the money to do that, since she's a student. It also doesn't adequately explain adequately how or why she would choose to work on her thesis (on her laptop) in a house without electricity. Having several batteries is not only very expensive, but you have to take the laptop and wait for many hours to get them all recharged. Then there's Heather's serious illness -- she has a rather unbelievable response to that, as well.
I'll probably give up and buy the next book in the series to find out what happens with all those plotlines (don't expect resolution of any plot lines in this book), but it's annoying -- but I guess it sells books.