In my opinion The Citadel of the Autarch is a nice and fascinating book. It's the fourth part of The Book of the New Sun series.
I like this series very much. All the books are interesting and worth reading, if you like Gene Wolfe's writing style. There are some people who don't like Gene Wolfe, but I like his books.
If you've read the other parts and liked them, I can recommend this book to you.