[zeroboy]

I did something like this writing my first book Zero to Superhero: http://zerotosuperhero.com

I'd wake up a 3 am every morning (except Sunday) and write until about 6 am, which is when I got ready for my 7 am shift.

I agree with the author that being super-motivated was key and I had already invested several years research and writing the book. I was becoming worried the book would never get done.

I was also able to avoid cognitive burnout because my day job was at a metal foundry and consisted of mostly repetitive work.

One drawback was I was completely zonked by late afternoon, and had no social life, but I still tried to eek out something for the book before bed (which was sometime between 8-9 pm if I remember correctly).

Afterthought: I can't wake up so early now. Lack of sleep gives me a short temper. Something to consider.