Azure Function returning a list of Book objects

BooksFunction.cs

public static class BooksFunction
{
  [FunctionName("BooksFunction")]
  public static IActionResult Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)]HttpRequest req, TraceWriter log)
  {
    log.Info("C# HTTP trigger function processed a request.");

    return new OkObjectResult(GetBooks());
  }

  public static IEnumerable<Book> GetBooks() 
    => new List<Book>
    {
      new Book(1, "Enterprise Services with the .NET Framework", "Addison Wesley"),
      new Book(2, "Professional C# 6 and .NET Core 1.0", "Wrox Press"),
      new Book(3, "Professional C# 7 and .NET Core 2.0", "Wrox Press")
    };
}