何～（なん～）— what
これ は 何 の 本 ですか。
What is this book about?
何～なん～
what
なん～
accent [1]In detail
Words
これkorethis
はwa(topic marker)
何nanwhat
のno(links the topic or type to 本)
本honbook
ですdesu(polite sentence ending)
かka(question marker)
Kanji
何カ・
何 is read なん in 何の本. The question asks what kind of book it is or what it is about. Other combinations may use なに, so learn the reading with the expression.
Coco-sensei