Define Hybrid Novels

I've been having trouble defining hybrid novels so I'll post some stream of consciousness here.

Basically I got the term "hybrid novel" while searching for The Invention Hugo Caberet by Brian Selznick and trying to find what genre it belonged to, since it wasn't a comic book as such but it wasn't an illustrated novel either because you couldn't just take out the images and still have it make sense. Graphic novel is how it is most often described but graphic novel has a fairly wide range of definitions, the genre encompasses comic books, sequential images without words and in some cases picture books. I played with the idea of defining it as "Unconventional Graphic Novels" but there are a lot of graphic novels that are unconventional and not all of them are a combination of prose and image, like I want. I found the term Hybrid novel from Zoe Sadokierski in her thesis Visual writing : a critique of graphic devices in hybrid novels from a visual communication design perpsective. She defines Hybrid novels thus: 
"Novels in which graphic devices like photographs, drawings and experimental typography are integrated into the written text. Within hybrid novels, word and image combine to create a text that is neither purely written, nor purely visual."
Which is exactly the description I'm looking for but apparently the books I have chosen lie on the fringe of the hybrid novel novel genre because they are also childrens/young adults books and can be defined as picture books. She does say that there are plenty of grey areas and its up to the readers discretion in these cases. 
Another concern I have is that The Savage fits more into the realm of post-modern picture book than hybrid novel. Certainly, if it had been a novel for adults it could easily fit into the hybrid novel category but as its for young adults it could go either way.