I came across an add every 5 to 6 pages of a novel I started this weekend. I got 2 points per ad, which doesn't seem like a lot to me considering the exchange value of rewards. 20k coins for a week of free reading would require you to watch 10k ads (for 2 coins each) and that is if they appear every 5 to 6 pages. So you'd need to read something like 50-60k pages to be able to claim that reward. At least that's how I perceived it, I could be wrong.