text: import React, { Component } from "react"
  import { connect } from "react-redux"
  
  class BookDetail extends Component {
    render() {
      if (!this.props.book) {
        return <div>Select a book to get started.</div>
      }
  
      return (
        <div>
          <h3>Details for:</h3>
          <div>Title: {this.props.book.title}</div>
          <div>Pages: {this.props.book.pages}</div>
        </div>
      )
    }
  }
  
  function mapStateToProps(state) { //argument of app state
    return {
      book: state.activeBook
    } // map app state to props of THIS component
  }
  
  export default connect(mapStateToProps)(BookDetail)
  