Monologue and duologue are generally terms for performance aren't they? I'd class the Gilead excerpt a reported dialogue - there are two speakers in the remembered conversation.
As to raising questions right at the beginning - surely that comes down to taste in reading. You don't like questions raised at the start, which is fine - but I love it. Which means that yourhas a really simple answer. 'Some readers love it.' (And also some writers love to do it, and do it well.)I think this is an awful way of starting a novel or any other piece of fiction. Starting with dialog is confronting the reader with characters who haven't been introduced and challenging them imagine a context. Why would anyone want to do this?
I'll have a think about a novel that starts in a more rigidly defined form of dialogue and let you know if anything comes up. But I do think that one of the ways it's successfully done is by slightly altering the convention of dialogue. To make it reported or remembered for instance - as above.