EF many to many relationship in Web Api using swagger

Question

I have a problem when I'm trying to set the many-to-many relationship in EF Core, and catch the result in Swagger.

public class  Book
{
    [Key]
    public int BookId { get; set; }
    public string? BookName { get; set; }
}

public class  Publisher
{
    [Key]
    public int PublisherId { get; set; }
    public string? PublisherName { get; set; }
    public ICollection<BookPublisher? BookPublishers { get; set; }
}

public class BookPublisher
{
    [Key]
    public int BookPublisherId { get; set; }
    public int BookId { get; set; }
    public int PublisherId { get; set; }

    public Book? Book { get; set; }
}

In the DbContext, I have:

DbSet<Publisher>? Publishers { get; set; }
DbSet<BookPublisher>? BookPublishers { get; set; }
DbSet<Book>? Books { get; set; }

protected override void OnModelCreating(ModelBuilder builder)
{
    builder.Entity<Publisher>().ToTable("TAB_Publisher", "dbo");
    builder.Entity<BookPublisher>().ToTable("TAB_BookPublisher", "dbo");
    builder.Entity<Book>().ToTable("TAB_Book", "dbo");
}

public List<Publisher>? GetPublishers()
{
    if (Publishers != null)
        return Publishers
               .Include(s => s.BookPublishers).ThenInclude(s => s.Book)
               .ToList<Publisher>();
    else
        return null;
}

When I call my method GetPublishers in Swagger, I get exactly what I wanted:

[
  {
    "PublisherId": 1,
    "PublisherName": "Publisher1",
    "BookPublisher": [
      {
        "BookPublisherId": 1,
        "BookId": 1,
        "PublisherId": 1,
        "Book": {
          "BookId": 1,
          "BookName": "TEST1",
        }
      },
      {
        "BookPublisherId": 2,
        "BookId": 2,
        "PublisherId": 1,
        "Book": {
          "BookId": 2,
          "BookName": "TEST2",
        }
      },
    ]
  }
]

How can I get the same result with the book? A book can have several publishers. What kind of relation do I have to set up?

Here is my cdm enter image description here