First, as I'm new to this forum, let me say hello and thank you for listening. A strange question: Is there any such thing as an unmarketable concept? Example: I've written a middle-grade SF novel set in the 1950s. It's set up to pay homage to the youth-targeted films of that period, many of which were SF. The protags are typical 50s kids who discover a monster roaming the hills near their small town. There's more to it, of course, but you get the idea. The novel is on the query train now. The trouble is, no one seems excited about the premise. One person told me that historical sci-fi (aside from Steam Punk) is almost an oxymoron and thereby unsellable. What are your thoughts?