FixedCode

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

public class BookLibrary
{
    public static void Main(string[] args)
    {
        int input = int.Parse(Console.ReadLine());

        Library library = new Library();

        for (int i = 0; i < input; i++)
        {
            string[] command = Console.ReadLine().Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
            string title = command[0];
            string author = command[1];
            string publisher = command[2];
            string releaseDate = command[3];
            string isbn = command[4];
            decimal price = decimal.Parse(command[5]);

            //идеята е че можеш да направиш всичко тук
            //когато ти подадат нова книга проверяваш дали вече има такък автор
            //и ако няма създаваш нова книга и я пъхаш в библиотеката
            //обаче ако има трябва да намериш книгата чийто автор е същия от входа и да я ъпдейтнеш
            Book book = null;
            if (!library.Books.Any(b => b.Author == author))
            {
                book = new Book(title, author, publisher, releaseDate, isbn, price);

                library.Books.Add(book);
            }
            else
            {
                book = library.Books.First(b => b.Author == author);
                book.Price += price;
            }
        }
        //var results = library.Books.Where(a => a.Author.Equals(a.Author)).Distinct();

        //bookAuthors.OrderByDescending(b => b.Value).ThenBy(a => a.Key);

        foreach (var item in library.Books
                                    .OrderByDescending(p => p.Price)
                                    .ThenBy(a => a.Author))
        {
            var authors = item.Author;

            Console.WriteLine($"{authors} -> {item.Price:f2}");
        }

    }
}
public class Library
{
    public string Name { get; set; }
    public List<Book> Books { get; set; }

    public Library()
    {
        Books = new List<Book>();
    }
}

public class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
    public string Publisher { get; set; }
    public string ReleaseDate { get; set; }
    public string ISBN { get; set; }
    public decimal Price { get; set; }

    public Book(string title, string author, string publisher, string releaseDate, string isbn, decimal price)
    {
        this.Title = title;
        this.Author = author;
        this.Publisher = publisher;
        this.ReleaseDate = releaseDate;
        this.ISBN = isbn;
        this.Price = price;
    }
}