Create extreme urgency.
On your sales page, after the headline, show a floating countdown timer with the price. The price is heavily discounted and goes up very quickly (5–15 minutes?) until reaching the full price. The timer shows how much time until the next higher price is set. This floating overlay follows the buyer as he scrolls and reads through your sales letter. The timer does not have to be the same for each step nor does the price increase, but the buyer can see what the next price will be. For instance, the first or last timers can be longer. You can also have a final timer after reaching the full price, where you give the buyer some extra time to buy it full price but also get a bonus. You might want to use this tool only on the second visit of the customer.
It might be the clincher for the deal.
When advertising your online product or service, use the unconventional bonus of food (like special brownies, gourmet cheese, etc.) Unless you are already selling food online, and if food is very distant from your product, this might make a big difference.
Build a game around each chapter of the book. For instance, after reading the first chapter, the reader has to realize what is the most important word, sentence, concept, etc. in that chapter. He then has to communicate this (website, email, SMS, etc.) to you. If he is correct, he gets a bonus (an extra short story about the main character, a badge, a tip, etc.) If he is not correct or a bit off he’ll get some help to arrive at the right answer. Each chapter has a different game, and if they make it to the last one, they get a big bonus.
The objective is not to make it hard, but fun and rewarding, so they are motivated to continue and maybe also spread the word about it.