What is the difference in meaning between these two sentences, and when do I use each:
- Have you read the book yet?
- Haven't you read the book yet?
Purely in terms of a request for information, there is no difference between the two—the answer will produce knowledge of the fact if the book has been read.
However, there is a difference in the emotional tenor and context between the two.
1. Have you read the book yet?
Generally speaking, this is more of a neutral expression that is simply asking for information.
A week later, Jim met Jane again. "Have you read the book yet?" he asked her.
2. Haven't you read the book yet?
This would more often be used in the context of surprise—or even a negative emotion like condescension—and would probably be rhetorical, in the sense that it's already known they haven't read it yet, so no response is actually required.
Two months later, Jane casually told Jim, "I still don't know if she dies in the end."
Jim replied in shock, "Haven't you read the book yet?"