This is one of the best ebooks to learn react if you are a beginner.
 
Author: Favio Copes
 
Table of Contents:
Preface
Introduction to React
How much JavaScript you need to know to use React?
Why should you learn React?
How to install React React Components
Introduction to JSX
Using JSX to compose UI
The difference between JSX and HTML
Embedding JavaScript in JSX
Managing state in React
Component Props in React
Data flow in a React application
Handling user events in React
Lifecycle events in a React component
Where to go from here