I haven't written a book
per se, but I do tend to do a lot of scientific writing.
On a yearly basis:
6-10 papers that are roughly 40-50k words with 6-12 figures.
Several grants which are 20-30 pages with different formats but similar in length.
Heavily reworking undergraduate/graduate theses (usually 100-150 pages in length)
Small other stuff (short essays, etc...)
So roughly somewhere between 500-1000 pages/year depending on what's required.
I'm also working on a synopsis of my last 3-5 years or work which should weight in at roughly 3-500 or so pages.
During all of this I have found several things out that are absolutely critical to produce this volume:
1. What's the reason? Passion is essential. Hatred/angst will work as well. Just doing it because "I've always wanted to" isn't a good reason unless you're OK with producing a mediocre product. Personally, I think a "ghost writer" is kinda weak as it detracts from your input. However, I would establish a network of friends/colleagues/people in a similar position (with similar passions?) to read your work and PROVIDE CRITICISM/CRITICAL INPUT. A person who doesn't understand your vision/passion/angst is useless here.
2. Once the first compilation of the work in completed, you're about half-way done. Half to produce the initial text/figures, then another 50% to get it ready for submission/serious consideration. Most people are shocked by this. Here, I guess that you could hire someone to finish it, but I don't like letting hired people into my creative process.
3. You need to have a schedule. Is this a side project? Is this your "life's work?" Is this fun and you don't care if you complete it? Personally, I need to set aside a few hours per day to write (realistically, I need to produce 2-5 submission quality pages/day every weekday for an entire year to reach my goal.) I find that if I get up at 4am and make coffee and watch the news for an hour or so, that by 5am I can write for 3 hours until 8am, then have a normal workday until between 5 and 8pm. Without these few dedicated hours per day, it would be patchwork writing and would be not so useful. Maybe start with a dedicated hour or two per day.
There was a great article in The Guardian about Haruki Murakami and how he does it, here (I found it quite inspiring and 1Q84 well worth the read):
http://www.guardian.co.uk/books/2011/oct/14/haruki-murakami-1q84
4. Have fun. It's easy to forget this. But remain serious. Without seriousness, nothing would get accomplished. In addition, really busy people get much more done, because they don't relax. A classic example is Crime and Punishment, which was written to pay off a debt and was essentially uncorrected (
i.e. published as written once through with no revisions).
Good luck and I hope this helps!