BooksService to create the Azure Cosmos DB database, and read and write entities

BooksService.cs

public class BooksService
{
    private BooksContext _booksContext;
    public BooksService(BooksContext booksContext) => 
        _booksContext = booksContext ?? throw new ArgumentNullException(nameof(booksContext));

    public async Task CreateTheDatabaseAsync()
    {
        var created = await _booksContext.Database.EnsureCreatedAsync();
        if (created)
        {
            Console.WriteLine("database created");
        }
        else
        {
            Console.WriteLine("database already exists");
        }
    }

    public async Task WriteBooksAsync()
    {
        _booksContext.Books.Add(new Book { BookId = Guid.NewGuid(), Title = "Professional C# 7 and .NET Core 2.0", Publisher = "Wrox Press" });
        _booksContext.Books.Add(new Book { BookId = Guid.NewGuid(), Title = "Professional C# 6 and .NET Core 1.0", Publisher = "Wrox Press" });
        _booksContext.Books.Add(new Book { BookId = Guid.NewGuid(), Title = "Enterprise Services with the .NET Framework", Publisher = "Addison Wesley" });
        int changed = await _booksContext.SaveChangesAsync();
        Console.WriteLine($"created {changed} records");
    }

    public void ReadBooks()
    {
        var books = _booksContext.Books.Where(b => b.Publisher == "Wrox Press");
        foreach (var book in books)
        {
            Console.WriteLine($"{book.Title} {book.Publisher} {book.BookId}");
        }
    }
}