books doesn't work

using System.Collections.Generic;

internal class Program
{
    static void Main(string[] args)
    {
        Book book = new Book();
        List<Book> library = new List<Book>();
        book.WorkingProgram();
    }

    class Book
    {
        public List<Book> library = new List<Book>();

        public Book(string bookTitle = " ", string authorName = " ", int yearOfPublishing = 0)
        {
            BookTitle = bookTitle;
            AuthorName = authorName;
            YearOfPublishing = yearOfPublishing;
        }

        public string BookTitle { get; private set; }
        public string AuthorName { get; private set; }
        public int YearOfPublishing { get; private set; }

        public void WorkingProgram()
        {
            const string AddBookCommand = "1";
            const string FindBookCommand = "2";
            const string DeleteBookCommand = "3";
            const string ShowAllBooksCommand = "4";
            const string ExitCommand = "5";

            Book book = new Book();
            bool isWorking = true;
            Console.Write("Добавте книгу: ");
            book.AddBook(library);
            Console.Clear();

            while (isWorking)
            {
                Console.WriteLine($"Хранилище книг\n\n\n" +
                    $"Введите {AddBookCommand} если хотите добавить книгу.\n" +
                    $"Введите {FindBookCommand} если хотите найти книгу.\n" +
                    $"Введите {DeleteBookCommand} если хотите удалить книгу.\n" +
                    $"Введите {ShowAllBooksCommand} если хотите увидеть список книг.\n" +
                    $"Введите {ExitCommand} если хотите выйти из программы.\n\n" +
                    $"Ввод: ");

                string? userInput = Console.ReadLine();

                switch (userInput)
                {
                    case AddBookCommand:
                        book.AddBook(library);
                        break;

                    case FindBookCommand:
                        book.FindBook(library);
                        break;

                    case ShowAllBooksCommand:
                        book.ShowAllBooks(library);
                        break;

                    case DeleteBookCommand:
                        book.DeleteBook(library);
                        break;

                    case ExitCommand:
                        isWorking = false;
                        break;

                    default:
                        Console.WriteLine("Введена неверная команда.");
                        break;
                }
                Console.ReadKey();
                Console.Clear();
            }
        }

        public void AddBook(List<Book> _library)
        {
            bool isWorking = true;
            string? userInput;

            Console.WriteLine("Введите название книги: ");
            userInput = Console.ReadLine();
            BookTitle = userInput;
            Console.WriteLine("Введите имя автора: ");
            userInput = Console.ReadLine();
            AuthorName = userInput;

            Console.WriteLine("Введите год издания: ");
            bool isSucces = int.TryParse(Console.ReadLine(), out int result);

            while (isWorking == true)
            {
                if (isSucces == true)
                {
                    YearOfPublishing = result;
                    isWorking = false;
                }
                else
                {
                    Console.WriteLine("Нужно ввести число.");
                }
            }

            Book newBook = new Book(BookTitle, AuthorName, YearOfPublishing);
            _library.Add(newBook);
        }

        public void ShowAllBooks(List<Book> _library)
        {
            foreach (var book in _library)
            {
                Console.WriteLine($"{book.BookTitle} {book.AuthorName} {book.YearOfPublishing}");
            }
        }

        public void FindBook(List<Book> _library)
        {
            Book book = new Book();
            Console.WriteLine("Введите название книги или имя автора для поиска: ");
            string? userInput = Console.ReadLine();
            _library.FindAll(item => item.AuthorName == userInput);
            _library.FindAll(item => item.AuthorName == userInput);
            List<Book> foundBooks = _library;
            Console.WriteLine("Список найденых книг:");
            book.ShowAllBooks(foundBooks);
        }

        public void DeleteBook(List<Book> _library)
        {
            Book book = new Book();
            Console.WriteLine("Введите название книги или имя автора для удаления: ");
            string? userInput = Console.ReadLine();
            _library.RemoveAll(item => item.AuthorName == userInput);
            _library.RemoveAll(item => item.AuthorName == userInput);
        }
    }
}