Neither is better, I've seen stores be more successful on Amazon and others more successful on their own site. It depends who your audience is and how you market to them.
It's fairly easy to set up both, so I would do this:
1) List your book on Amazon to take advantage of all the traffic there.
2) Set up your home base on a Shopify site where people can buy there as well.
I've heard something like Amazon giving higher commission rate for listing their exclusively. I'm personally not a fan of exclusivity because it's not the best for the customer, but that's something you'd want to look into before making the decision.
Amazon hosts 20,000 Sprinter trucks. Wow, I'm glad this news. The promotion of the Amazon delivery site is very noticeable. They develop every month, and their development is visible in every movement. Let's say this event demonstrates their seriousness in purchasing goods. I personally love their zeal and the way they try to build their shipping site and make it as popular as possible. Also on Amazon delivery site I love their design. Very nice background design. The delivery itself is very good, the goods arrive safe and sound. Try it for yourself, this Amazon site also has Vont.