[Lain]

That's a fairly large amount of writing within a month. Do you get a prompt for a specific topic or constraints to follow, or do you more or less have the freedom to take it how you wish?

Basically full creative freedom. And since it's all basically public domain work, you can use copyrighted characters and write fanfics too as an entry, as they quote:

"If you believe you're writing a novel, we believe you're writing a novel too."

And eh, 1500 words a day isn't too bad. If you're not used to writing a lot (or if you don't read a lot either) then it might seem daunting, but 1500 words is 6 pages double spaced size 12, 1" margins. Double-spaced pages really aren't hard to write, takes me a couple minutes anyway, and if you already have your ideas in mind then it just gets faster.

The official contest rules state that it's only the writing portion that you can't do before the start; you can extensively plan out your novel and come up with story, characters, main events, etc. before the official starting date. So if you get started a week before with planning, then you can usually get through the month having written your 50k or more.
That's why there are so many people who participate haha.

EDIT: Apparently, the word count for The Time Machine (H.G. Wells) is just about 40k. It's an 80 page long book or so (or at least well below 100pgs for my copy) so 50k words would translate roughly into 100 regular book pages. None of the really long page types like the ones you'll find in Gravity's Rainbow or Infinite Jest or something, but typical, like Harry Potter (since I'm sure everyone's familiar with that.) I'd read that in probably a little less than two hours, so 2-3hrs is probably a good median range to get an idea of the length.

So if you go at it for an hour a day throughout november, you'd have written 30hrs worth of material, and of course reading is always faster than writing, but even if we boil down 90% of it from 30 to 3hrs, that's reasonably what we would expect.