"这是什么书？"

Translation: What book is this?

[deactivated user]

alternatively: 这个书是什么？

[Swansae]

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?"

[RobinThor]

"what kind of book is this" is not accepted

[Peter126850]

The pronunciation of "shu" sounds strange to me here. It sounds more like "shou".