The design that really caught my eye was this one featuring the cover from his Astronomica series:
If you have a blog or social media, you may have wondered how you can use it to make money. One way that many people make their living online is through affiliate referral links. Basically, you recommend products and services to your audience, and when they buy - YOU get a cut of the profits! This can be a great way to make some extra spending money, but some people have mastered the art of affiliate marketing and are able to travel the world just off the money they make from their social media accounts! Sound like a good idea? Read on!