Yesterday a friend of mine, on behalf of her younger brother, asked me how long it takes to write a book. Now, you know me by now, and so you probably already guessed that my snarky side immediately started typing "forty-two." Hey, it's the ultimate answer to everything, right?
Still, I restrained my snark. She's a friend, and a good friend's daughter, and had asked a sincere question that actually does have a real answer.
The only problem is that I don't know the answer.
The short version of the best approximation to a response that I know would be: "as long as it takes."
What is a book? More specifically, how long is a book? If you go by "industry guidelines," whatever the hell those are, a fiction book for a new author should be around 80,000 to 120,000 words. Because, you know, we new authors can't possibly, successfully, spin a complex tale.
(The real reason I've heard is that publishers aren't willing to risk more pages than what's required to hold120K words on an unknown author. It makes sense; publishers charge by the page no matter how many squiggly marks you want them to put on each. And standards, once set, are hard to change--a key measure of web site type size is based upon a several-hundred-year-old typographic standard in which there were a dozen dozen of them per French foot, and I've heard that our roads are the width they are based on the distance between Roman chariot wheels. Not that I'm suggesting books are going the way of the Roman chariot, but....)
Anyway, I aimed for this range in the three novels I have out now, Cataclysm, Ascension, and Deception, thinking that if I played the game according to "industry guidelines" I'd nab a lush publishing contract and launch myself toward my first million dollars in the bankie-pooh. Obviously it didn't work out that way, but it did result in three pretty good novels for sale on Amazon.
Thing is, you don't have room for much plot twisting in 80,000 words. At least, I didn't think so. I'm thinking I probably can do more now, and I am aiming for more in the first book of the Elf Queen series, which will still be in that word count range. My sci fi work in progress, meanwhile, is going to give a great big moist and loud raspberry to the "industry guideline" and present many more words, and a helluva twisted plot, for your reading pleasure.
So now that I've not-answered the question about length in word count of a book, the other significant variable is how many words you can bleed into a word processing program every day. Stephen King, in On Writing, says 2,000 is what you should go for, and I kind of agree with that. It's a significant chunk of writing, but it's attainable. At that pace, he says, you can finish a 180,000-word novel (more than the 120K max for newbs, but remember, he's not what anybody would call a newbie author) in ninety days, which is, give or take a holiday, three months.
So three months! There, you have it. It takes three months to write a book. More specifically, it takes three months to write a 180,000-word novel (a term which implies fiction as the genre category) at the pace of 2,000 words per day. It's just simple mathematics.
It took me just under two months to write Cataclysm.
It took me three months to write Ascension.
It took me nine months to write Deception.
Mathematics--you suck. I guess it just takes as long as it takes.
Keep in mind that another, hidden, variable is the revision time. If you're going to write a draft and send it out, expect a lot of negative feedback (then again, if you're going to revise the hell out of it and send it out, you should still expect a lot of negative feedback--ahh, the joys of authoring). But this hidden variable is the reason Karl Marlantes told us (at the 2011 James River Writers Conference) that it took him 25 years to write Matterhorn. Yes, there are a lot of words in that book, words that I still haven't entirely read through yet, but hopefully nobody is thinking it took him 25 years of just writing to create it. At 2.000 words per day, that's somewhere north of 18 million words. That's somewhere around 23.5 Bible-lengths.
That's a lot of words.
No, what his 25 years consisted of was writing the book and setting it into a drawer for a while, and then rewriting it. He said that at one point he had to revise out three entire pages talking about dirty socks--a vital topic to an Infantryman, but not so much to a novel reader.
Revise, revise, revise. How long does that take? Well, it takes as long as it takes. Cataclysm is on its eleventh major revision, and I'm thinking it's pretty darn good and done. Ascension required nine revisions to get where it is. Deception took seven.
See the trend? I'm excited; somewhere around my seventh novel they're going to start coming out better than the revisions can be.
*ahem* Once again I must say: mathematics--you suck.
Regardless, it really does get easier to write well the more you do it, an assertion I've made many times. The number of revisions you'll need to make will, in fact, decrease, though never quite to the point of being negative.
But back to the original question--let's assume you're talking about your first novel. Let's assume you can put out 2,000 words per day, and that your writing skill is approximately similar in level to mine when I began. Let's assume you're writing an "industry standard" length novel, rather than 23.5 Bibles.
All those assumptions made, then, it'll take a couple of months to complete the first draft, and another three to twelve to polish it up to where you like reading it.
Or in other words--it takes as long as it takes.