Questioning titles

How important is the title of a book? More specifically, what do you think about about using a question as the title of a book?  It can be an effective ploy, drawing attention to the book, and piquing the readers curiosity. Such titles are found most frequently in non-fiction or childrens book collections. But what about as a title for adult fiction? As you browse the library shelves, searching for something new to read, have you encountered many, or any, fiction books with a question as the title? Did the use of this ploy interest you, or even intrigue you,  and was it enough to make you want to pick up the book to read it? 
Although the question on the book cover would probably be rhetorical, would you still expect find an answer within?
Here is a selection of adult fiction books using a question as the title.  Which of these questioning titles would you like to read?

Do androids dream of electric sheep? Philip K. Dick
Remember me? by Sophie Kinsella
N or M? by Agatha Christie
Where are you now? Mary Higgins Clarke
Would I lie to you? Clare Dowling
Can you forgive her? Anthony Trollope
Who needs Mr Darcy? Jean Burnett
Why not? by Shari Low
Who's that girl? by Alexandra Potter

Can you think of any others?