The best excuse for an alternate history is that it makes a good story. There are two types of alternate histories that I enjoy. One type is an improvement on history. I really wish that history had gone the way the author describes in the novel. Some alternate histories that I've come across are dystopias. These are good stories if they provide a meaningful conflict with some insight into problems that we are wrestling with in our own timeline. I've reviewed a number of alternate history dystopias recently on Shomeret: Masked Reviewer.
The Book of Esther by Emily Barton is an alternate history of the first type. It would be wonderful if history had gone this way. Once upon a time there was a Jewish kingdom on the steppes bordering with Russia. It was called Khazaria. This kingdom actually existed, but in our universe it was overrun and destroyed during the medieval period. Its inhabitants scattered throughout Eastern Europe. Occasionally, you see Jews born with red hair. They probably have Khazar genes, but the culture of the Khazars has vanished. Now imagine that the Kingdom of the Khazars was still in existence during WWII and that Jewish refugees fled there. I was intrigued by this concept and received a digital galley for free from Edelweiss.
The Germans are poised to invade Khazaria. Esther, the protagonist, doesn't want to stand on the sidelines. She wants to help save Khazaria from the Nazis. The problem is that the Khazars are Orthodox Jews who expect women to aspire only to marriage and motherhood. She has an arranged engagement to a childhood friend. She would be happy to marry him under normal circumstances, but the situation for Khazars is far from normal. So Esther sets out for the legendary village of the Kabalists ,who are Jewish mystics and magicians. She hopes to ask them to change her into a man. Nothing happens as Esther expects, but she does discover that she can play an important role in saving Khazaria. This is definitely the sort of female central character that fans of this blog want to hear about.
Since I am one of the ideal readers for The Book of Esther, I loved it. It's obviously intended for readers who are very well-educated in Judaism. Jewish customs and religious terminology aren't explained. Neither is the structure of Khazar society. So if you've read about the Khazars, as I have, you will also have a leg up in understanding who is who in this novel. A glossary and recommended bibliography would have been very useful for many readers who have professed themselves mystified in their Goodreads reviews of this novel. I'm not sure why Barton would have purposely narrowed her audience.
If you're inclined to research the books you read, I think that Barton's book will reward you for this effort. Esther is a courageous and intelligent heroine, and there is one rather surprising character that she encounters among the Kabalists. I highly recommend this book.