When is a book not a book?

The interesting thing about Amazon is that everything that is sold in their books section is classed as a book. No matter whether it's a single sheet of A5 with one word on it or the complete works of Tolstoy.



So, should there be a separate nomenclature for shorter works of fiction? I appreciate we have terms like: short story, micro fiction, nanofiction and so but they are still clumped together under the term 'Novel' or 'Novella'.



When I buy a novel I expect about 80,000 words or in laymans terms 'a good long read', when I buy a 'novella' I expect a 'good short but punchy read'. Short stories, microfiction and nanofiction are often collected into a single work and called 'a collection of...' therefore I expect another 'good long read of different stories.'



But what if what I'm writing doesn't fit neatly into those categories? I don't have enough words to call it a novel or a short story and I don't have a collection of them to bundle together. The buyer then feels short changed when they are buying my story and may not return to buy my work again.



I now want to publish the e-booklet. A single work of fiction that leaves the purchaser under no illusion that what they are getting is a very very short story. But then do we have further subcategories such as e-pamphlet, which would be smaller than a booklet?