Nicoleandmaggie asked "Is there a test you can take to see if you're with book or not?"
This is precisely the question I have. How do you know when you're writing a book?
I haven't done this before. I did not turn my dissertation into a book. It was conceived as a series of linked studies, discussions of the way a single theme worked in multiple texts. I mined it for articles (one good one, part of another, one bad one that never got published), and got tenure by writing articles. I'm not exactly an article-producing machine, but I do have a good idea of how to write an article and what one looks like.
Over the years, I have planned two books (two different takes on the main idea, since there came a point where it seemed the first version wouldn't work), and worked on them in fits and starts: a conference paper here, another there, chapter "dump files" on my laptop into which I put quotations and insights I hope to use in that chapter. These files are not even zero-drafts, just a place to collect bits and pieces. For the last couple of years, I have been trying to clear the decks of various articles in various stages of production so that I could stop being distracted by such unfinished material and work on the latest version of the Putative Book as my sole project.
So this summer's article project was supposed to be part of that deck-clearing. I did not expect a conference paper to turn monograph-sized. But having finished writing up the first section of my outline and coming in around 6000 words this morning, either I am being incredibly long-winded, or I'm looking at a longer project.
Five chapters of around 6000 words each would be 30K words. I'm looking a friend's monograph, 128 pages before the notes and bibliography. Assuming 250 words to a page, that's 32K words. I think I'm in that ballpark.
So what's the test? How do you tell? How and when did you, gentle readers who have written books, know that that was what you were doing?