Here's an always informative and thought-provoking subject from the Fictionautics:
On Speculative Fiction, Science Fiction and Genres
This article focuses on informing readers what falls into what genre (or the best guess) and why.
As a writer, I struggle with how to pitch my work. The boundaries that define many of the genres and subgenres are blurred at best. If I describe my novel as "near future military science fiction romance with paranormal elements," most agents or editors won't read past the first line. Calling it simply speculative romance, slipstream or paranormal romance doesn't begin to give a sense of the elements of the story. I normally fall back on science fiction romance and then try to cover or at least hint at the other elements in the pitch paragraph.
So why even have genres?
Doing away with genres altogether creates a new set of problems. As a reader, I want to be able to filter or search for books that tend to have science fiction romance elements (even though when I execute that search, I often get novels that I'd categorize as pure fantasy). If there are no genres, will I have to sift through thousands of titles and blurbs to find the type of story that interests me?
So we struggle with genres, subgenres and cross-genres as best we can. The author of the article made a point that I agree with. When writing, don't restrict creativity to labels. Just write it and worry about pidgeon-holing it later.