When someone say "you must like a book", the meaning is....
1. It is 100% certain that you like a book

2. You have to, should like a book, You are foreced to like a book.

3. It depends on a context.

Which is correct among 1~3

^^

Question

When someone say "you must like a book", the meaning is....
1. It is 100% certain that you like a book

2. You have to, should like a book, You are foreced to like a book.

3. It depends on a context.

Which is correct among 1~3

^^

Answer

I think it means "logically, based on what I know about you, I deduce that you will like this book."

For example;
1. You like the style of mystery known as "English mysteries."
2. Elizabeth George writes English mysteries.
3. Therefore, you must like Elizabeth George's books.

"Must" is used in the sense of "logical necessity," not "force" or "obligation."

It is not 100% certain. There are at least two ways the reasoning could fail.

a) You might be wrong about my liking English mysteries in general.

b) Elizabeth George was born in, educated in, and lived for decades in Southern California. I might not agree that her books really qualify as "English mysteries."

(P.S. I love Elizabeth George's books).

Answer

"I see you reading that book every day. You must really like it."

It means that I think that you like it, based on what I know. It's a way to start a conversation, and the other person would say, "yes, I really do!" Or, "well, not really, but I have to read it for class."