Yes, it’s not an actual book if I’m not in excruciating pain 
More seriously, I was talking about getting something out of the book (besides entertainment), usually in the form of appreciating the writing style (貝に続く場所にて | L41 randomly comes to mind), but a non-fiction book will literally teach me things.
I think the term you mean is “エンタメ小説” - “ライトノベル” is a much more specific thing.
or maybe 大衆文学 is the “proper” term?
大衆文学 is the formal term, yes, but it’s indeed different from a light novel. For instance, 容疑者Xの献身 | L34 (and other books by that author generally, but that’s one I read) is considered 大衆文学, but it is head and shoulders above a light novel, so I consider it to be a different category (and I’m counting it as a “proper” book when it comes to my own stats).
To repeat myself, what I mean by light novels are literal light novels plus
Somehow, an editor decided that “nah, that goes in the other bin”, but that’s a subjective line.
