That's definitely up to you. The second chapter of this book shares a lot of the fundamentals in one of the earlier chapters in Fullstack React on core concepts of the React API. However if you feel like you would benefit from learning how to build web applications with React first - that can definitely be a better starting point. Otherwise if you're considering building iOS/Android apps with RN without much prior experience with React, this book will be just fine as we don't expect our readers to be proficient with React :)