The second book, The Secrets of Heavenly, is a book that I am currently reading, and have not decided if I will have him read it. It is quite a bit more graphic than 12 Years A Slave, but a very good book. Apparently this is the first book in a series. I await the next book to be released. If you have Kindle Unlimited this book is offered for free reading right now.
I also have Uncle Tom's Cabin, on the list, but I have tried to read that one several times and just can not get into it. So, I am not sure I will use that one.