What's currently in the alpha? The current alpha contains about 15 hours that represent around 20% to 25% of the content of the final game, depending on your play style. Take this with a grain of salt because that really is an average. Some players will take three times as long, others might finish the game faster.
I don't have a source for the level 20 as max level comment yet. I think that was made during the kickstarter. I should reword that statement because I'm not sure that's set in stone.
