“The defining factor of so many books is Genre. It’s an excellent way to find the stories you want to read, to find community who shares your literary wishes. You know how it is, you’re talking to a co-worker and discover you both love reading. Giddy with the connection you ask what they are reading, and then it’s crashing disappointment when you discover their deep love is True Crime and you’re all about hard Sci-fi. Sure your Aunt May reads constantly, but it’s all Mysteries and you’re not interested in those so much, even if you’ve read a few you like.”
read more about the difficulties of branding a book with a particular genre via Can you tell what it is just by looking? | Ajax Bell.