CategoryMappingProfile.cs

using BooksWebApi.Entities;
using AutoMapper;

namespace BooksWebApi.Models
{
  public class CategoryMappingProfile : Profile
  {
    public CategoryMappingProfile()
    {
      CreateMap<Category, CategoryModel>().ForMember(a => a.Books, opt => opt.ResolveUsing(c => c.Books))
      .ReverseMap();
      CreateMap<Book, BookWithoutCategoryModel>()
      .ReverseMap();
    }       
  }
}