My mom introduced me to Lewis' books years ago with The Shunning and I have been a fan ever since! Her Abram's Daughters series is my favorite so far, but I am for certain loving the Courtship of Nellie Fisher books. The Forbidden is book 2 in this "wunderful gut" series and it was a great read. Some of the themes here are the same as seen in other books by Lewis. The stories are set in the Amish world and deal with the struggle between being plain or fancy, but what I am enjoying with this series is the view of Old Order and New Order Amish.
In previous books it seems that the Amish society is very black and white... if you don't believe as they do and live by their rules, then you are out... shunned. But in the Courtship books, we see a group of Amish who choose to live as the Amish live, but have learned the truth of salvation by grace and embrace it fully. They are the New Order Amish and, at least in this bit of fiction, they are not being forcibly banned from their friends and family. Although there are some who are shunning them out of their own fear and ignorance.
Nellie's family is one that has joined the New Order, all except Nellie who is determined to stay true to the Old Order and her beau, Caleb Yoder. But Caleb's father doesn't care about their love or Nellie's determination. He threatens to disinherit Caleb if he continues to court Nellie.
Families and friends are at odds with each other over the New Order.. which has within itself a split. There are those who are committed to live the Amish way, but with their new faith in Jesus as their Savior and others who want to go further and accept not only Jesus, but some of the ways of the modern worlds such as cars and electricity and the likes.
The Amish are so often seen as a peaceful people with no strife or conflict, but if Lewis' books are true to their character (and I believe they are) then the world's view of the Amish is tainted. They struggle with many of the same issues we all struggle with... faith... obedience... temptation... and the outcome of their struggles are often life changing.