Ebook writing is a multi-billion industry making it one of the most profitable ways to make money online. Here's how you can augment your earnings from this endeavor: 1. Sell ad spaces. Before you publish your ebooks, scour the internet and find interested marketers who are willing to pay you for ad spaces. Let them know the benefits that they can get in advertising their products on your ebook pages and how it can help them boost their sales and revenue without really burning their pockets for their advertising cost. You need to ensure that these people are selling products that are closely relevant to your main topic.