I've seen some books and courses claiming that books could be written in 30 days, a week, a weekend, 3-1/2 days or even "a bestseller in a day or less." I usually recommend six months.
I'm conducting an experiment to see if I can write, edit and format an inexpensive but useful e-book book in two days. The title is "Writers Can Get Away With Apparently Absurd Tax Deductions That Ordinary People Can’t."
This book will tell you what you can probably get away with, and also provides important basic advice on business and taxation .
I'm now on page 52 and expect to finish at around 110-150 pages.
I normally wake up at 3:30. It's now past 1 AM. I started at 1 PM. I'm going to bed for a while.
I am a tough taskmaster.