Because I feel not enough people hate me, I thought I'd offer some comments about genre.
Genre is defined by various acknowledged plot devices. Mysteries have a crime to solve. Romance has a relationship to bloom. SF has a future or alternate world to explore. A pedant can get arbitrarily picky about the definitions and go looking for exceptions until it seems no definition fits any genre, but the clear reality is we all know genre when we see it.
The only type of writing which doesn't get boxed into a genre is literary fiction. It's always surprised me that people don't consider literary fiction to be a genre in its own right. Surely literary fiction is the genre in which nothing much happens?
By definition, if something interesting happens -- a murder, a romance, a war, a conspiracy, a plot to destroy the world -- then the book falls into one of the genres, and so it's not "literary", with the implication it's not as well written as if it were literary. Which is ridiculous because I have rarely come across a literary novel I considered as well written as the best genre novels, and when I have it was because the literary was among the best of its own kind. All that means is a top quality book is just as good as any other top quality book irrespective of genre, and a cruddy book can't be saved by being literary.
The SF writer Orson Scott Card talks in his excellent and perceptive books on writing about what he calls the MICE quotient: Milieu, Idea, Character and Event. His idea is these four attributes characterize any given story. Every story carries all four attributes of course, but in differing degree and mix. Mysteries and SF tend to be Idea stories: there's an intellectual problem to solve. Military adventure tends to be driven by the grand event, usually a war. Fantasies often exist only to show off their world: they are predominantly Milieu stories. In fact most books major in one of the MICE attributes, minor in a second, and the remaining two trail along.
In this scheme the mysteries of Agatha Christie are Idea first, Character second, followed by Milieu and Event. Solving the intellectual problem of the crime is always dominant for her, and she peoples her stories with all manner of eccentric characters. The milieu may add to the charm but is much less a consideration. Grand events play almost no part in her stories.
The MICE categorization of my historical mysteries is probably Character first, Milieu second, then Idea, with Event trailing a distant fourth. That's despite me writing a genre in which the mysery to solve would normally be dominant, but I know from reader feedback that my characters steal the show, and the unusual period I'm writing in becomes almost a character in its own right. This is only my own guess and if any of my early readers see this I'd be fascinated to know what MICE quotient you'd give me.
Orson Scott Card's idea makes a great deal of sense to me. Note that it does away with genre altogether and is much more about the style of the book rather than the plot devices.
I suggest most people are consistent in their preference for books with a given MICE categorization, at least by the first two letters. For example an IC book is probably (but not certainly) either SF or a mystery. Is there a strong cross-over between SF and mystery readers? Yes there is.