Исправление ошибок

#include <iostream>
#include <string>
using namespace std;
 
class BOOK 
{
    public:
    string author_full_name;
    string book_title;
    int number_of_pages;
 
    void set_book(){
        cout << "Add author to the list(Full name): " << endl;
        cin >> author_full_name;
        cout << "Add title of the author's book: " << endl;
        cin >> book_title;
        cout << "Add number of pages in the book: " << endl;
        cin >> book_title;
        return;
    };
 
    void get_book(){
        cout << "Author's full name is: " << name << endl;
        cout << "His book title is: " << title << endl;
        cout << "Number of pages in the book is: " << num << endl;
        return;
    };
            
        BOOK();
            name = author_full_name;
            title = book_title; 
            num = number_of_pages;
        
        ~BOOK() {
            cout << "Ohh... Did you just throw out the book?" << endl;
        };
    
 
    private:
    string name;
    string title;
    int num;
};
 
int main()
{
  BOOK first;
   switch(menu){
     case 1: 
         set_book();
         break;
     case 2:
       get_book();
       break;
     case 3:
         break;
     default:
     cout << "Error." << endl;          
    }
  cin.get();  
    return 0;
}