Question

There are many pictures......this book

Answer 1

The correct statement is -------There are many pictures in this book.

"IN" is a preposition used to denote the location of something.
"IN" refers to a particular noun in a specific space ( an enclosed space which is closed from all sides ). In layman terms, it means something is inside something that is taken into consideration.

Following are some examples,

In a bag.
In a hall.
In a nation.

Answer 2

There are many pictures in this book.
This is the correct sentence. Preposition In is used in linking noun, pronoun or noun phrase to some other part of the sentence.
Generally In is used to indicate position or location within or inside something.
In is also used to show relationship between someone or something to another thing.