Error loading schema when using a private constructor

[RomaKV]

The class Book contains two constructors. The first constructor is private with no parameters. The second constructor is public with parameters.
https://github.com/RomaKV/TestHotChocolate

    public class Book
    {
        public int Id { get; private set; }
        public string Title { get; private set; }
        private Book(){}
        public Book(int id, string title)
        {
            Id = id;
            Title = title;
        }
    }

The schema cannot be reloaded. Continuously reported: "Retry schema fetching".

Startup.cs

public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
            services
                .AddGraphQLServer()
                .AddQueryType<BookType>()
                .AddMutationType<MutationType>();
        }

BookType.cs

public class BookType : ObjectType<Book>
    {
        protected override void Configure(IObjectTypeDescriptor<Book> descriptor)
        {
            descriptor
                .Field(f => f.Title)
                .Type<StringType>();
            descriptor
                .Field(f => f.Id)
                .Type<IntType>();
        }
    }

Mutation.cs

    public class Mutation
    {
        public async Task<Book> AddBook(int id, string title)
        {
            return new Book(id, title);
        }
    }

MutationType.cs

public class MutationType : ObjectType<Mutation>
    {
        protected override void Configure(
            IObjectTypeDescriptor<Mutation> descriptor)
        {
            descriptor.Field(f => f.AddBook(default, default));
        }
    }

If the constructor Book(){} becomes public, the schema will be loaded successfully.

  public class Book
    {
        public int Id { get; private set; }
        public string Title { get; private set; }
        public Book(){}  // private doesn't work
        public Book(int id, string title)
        {
            Id = id;
            Title = title;
        }
    }

But, I can only use the private constructor no parameterless.
Why can't private constructors be used?
Please tell me how to get around this limit.

[michaelstaib]

The issue in your example is that you are using BookType as the query type.

The GraphQL root types must provide a public constructor or you can provide a custom DI registration in which case we will use your DI registration instead of looking for a constructor.

Why are you using book as a query type, this makes not really sense.