alternatively: 这个书是什么?
That has a slightly different meaning, and implies that you don't know what a book is xD
“这个书是什么” means "what is this book" in a very general sense, whereas “这是什么书” means more of "what kind of book is this?"
"what kind of book is this" is not accepted
The pronunciation of "shu" sounds strange to me here. It sounds more like "shou".