This book assumes previous knowledge of web development using JavaScript and Node.js. While you have many options of programming languages to develop a serverless application, all code examples of this book uses Node, so some basic knowledge of Node.js is necessary at least to understand how npm and the JavaScript ES6 syntax are used.
There are many cloud providers that offer serverless services, but this book focuses on AWS. You don't need to have prior knowledge of AWS because we will cover the basics too, but you will need to create an account to develop and test the code examples. If it is a brand new account, AWS offers a free tier of 12 months for you to learn and develop without any cost.