I totally agree that Stripe is easy to get started with and I believe their documentation is the best in the industry. But, as someone who processes payments in the six figures annually with Stripe, I feel there is definitely still room for a book like Pete's, in the same way that there was a place for a book about design patterns even among talented and experienced developers. His book builds on the platform, rather than replacing the documentation.

I manage a drop-in Rails engine for adding Stripe subscriptions to an app (http://github.com/andrewculver/koudoku) and the number one piece of feedback I get is that people wish they had heard of it before they integrated Stripe subscriptions in their app. This tells me that there is room for gems like mine and books like Pete's in the little ecosystem Stripe has created.