Novel.

[chin85]

What makes a book a novel?

[LeMarchand]

It has to be of a certain length and be fictional.

[Sludge]

Nothing. Regarding novels:-
(1) Novels are, at least partially, intended as entertainment.
(2) The subject matter is presented as fictional even though parts of it may be factual.
(3) The subject matter is familiar, credible and plausible, that is, the places and characters are believable to the readers.
(4) The subject matter is individual beings (usually human), their actions and relations; the novel places the individual at the center of the story.
(5) There are a small number of central characters.
(6) A single plot, however fragmented and tangential, unites the events and characters.
(7) The main character(s) evolves and grows over the course of the novel; the characters are �round,� or more fleshed out, than the �flat,� one-dimensional characters of earlier literary genres.
(8) Novels are set during an identifiable historical time period.
There are, of course, exceptions to each of these traits and a text need not meet all of these criteria to be considered a novel. Novels are sometimes contrasted with romances, but the original concept is similar, hence the French word for "novel" is "roman". The first "Romantic fiction" was usually fantastic, set in a mythical ancient time, and had shallow characters. The term has now come to refer to popular fiction where a love story takes centre stage, often at the expense of characterisation an

[Sludge]

Books are a:-
1. bound collection of pages: a collection of printed or manuscript pages sewn or glued together along one side and bound between rigid boards or flexible covers
2. published work: a published work of literature, science, or reference, or one intended for publication
3. bound set of blank sheets: a bound set of blank sheets of paper, for example for writing in
4. set of things bound together: a set of objects, for example, matches or fabric samples, that are bound or otherwise fixed together
5. division of literary work: each of several major divisions of a literary work, or of the Bible
6. set of rules: the body of rules or procedures relevant to a situation
likes to do things by the book
7. bookmaker�s record: a record kept by a bookmaker of the bets made and of the money paid out
8. script or libretto: the script of a play, or the libretto of an opera
9. card games number of tricks needed in scoring: the number of tricks that need to be won by a player or side in order to be scored
10. imaginary record: any imaginary record, archive, or repository of knowledge
11. sports record about sports opponents: in sports, a record of facts and information about the strengths and weaknesses of a player or team
12. book  or Book Bible: the Christian Bible or Hebrew scripture
13. accounting financial accounts: the financial records and accounts of an organization

[srd]

Do you mean when does a collection of bound pages qualify for being a novel, or what differentiates a novel from a short story, epic poem, etc.? The former has been pretty thoroughly answered by Sludge (though postmodern writing blurs even some of these boundaries), the latter needs a lot of discussion!

[incuriam]

http://www.fictionfactor.com/articles/wordcount.html