Db

 public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Surname { get; set; }
        public string Auth { get; set; }


        public virtual ICollection<Book> Books { get; set; }

        public User()
        {
            Books= new List<Book>();
        }
    }
 public class Book
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Year { get; set; }
        public int Auhtor { get; set; }
        public string PathImage { get; set; }

        public virtual ICollection<User> Users { get; set; }

        public Book()
        {
            Users = new List<User>();
        }
    }
public class UsersContext:DbContext
    {
        public DbSet<User> Users { get; set; }
        public DbSet<Book> Books { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Book>().HasMany(c => c.Users)
                .WithMany(s => s.Books)
                .Map(t => t.MapLeftKey("BookId")
                    .MapRightKey("UserId")
                    .ToTable("BookUser"));

        }
    }
  public class BooksDbInizializer:DropCreateDatabaseAlways<UsersContext>
    {
        protected override void Seed(UsersContext context)
        {
            List<Book> books = new List<Book>();
            User u1 = new User { Id = 1,Name = "Alex",Surname = "Kleandrov"};
            User u2 = new User { Id = 2, Name = "Alina", Surname = "Platonova" };
            User u3 = new User { Id = 3, Name = "Alex", Surname = "Ivanov" };
            User u4 = new User { Id = 4, Name = "Irina", Surname = "Kleandrova" };
            List<User> users = new List<User>();
            users.Add(u1);
            users.Add(u2);
            users.Add(u3);
            users.Add(u4);
            foreach (var user in users)
            {
                context.Users.Add(user);
            }

            books=JsonConvert.DeserializeObject<List<Book>>(File.ReadAllText(@"JsonBook.json"));


            Random rnd = new Random();
            foreach (var book in books)
            {
                book.Users.Add(users[rnd.Next(0,4)]);

                context.Books.Add(book);
            }


            base.Seed(context);
        }
    }