A question out of the blue is one that begins a topic of conversation; no previous information is presupposed. In the conversation below, if the first speaker had used a Perfective verb (ВІ прочитђли ітот ромђн?), there would have been some sort of presupposition, like, for example: "I assigned this book for you to read; have you finished reading it?"
— ВІ читђли ітот ромђн? "Have you ever read this novel?"
— Нљт, не читђла. "No, I haven't."
— Кђк ћн назывђется? "What's it called?"
— «Войнђ и мќр». "War and Peace."
— Ктћ егћ написђл? "Who wrote it?"
— Егћ написђл Толстћй. "It was written by Tolstoy."
For questions out of the blue, use Imperfective verbs, as in ВІ читђли ітот ромђн? (At the end of the above conversation, when more specific information is asked for, the Perfective is used: Ктћ егћ написђл? — not a question out of the blue.)