GroupJoin and Include

GroupJoin之后我想包含Book。作者，因为田野的书。作者将为空。但是我不能。我该怎么做才能解决这个问题?

Queryable<NewRead> recent = Repository.NewReads.Where(x => x.UserId == usersId);
var newFavs = IsAuthorized ? Repository.NewFavs.Where(x => x.UserId == UserId) : Repository.NewFavs.Where(x => false);
var recentFavorite = recent.GroupJoin(newFavs,
                             x => x.BookId,
                             y => y.BookId,
                             (x, y) => new {Recent = x, Favorite = y, x.Book});

I tried:

var recent = Repository.NewReads.Include("Book.Authors")
                   .Where(x => x.UserId == usersId);

和

var newFavs = IsAuthorized ? Repository.NewFavs.Include("Book.Authors").Where(x => x.UserId == UserId) : Repository.NewFavs.Where(x => false);

和所有这些放在一起。它在GroupJoin之前工作，但在Authors字段丢失之后。如果我添加:

var recentFavorite = recent.GroupJoin(newFavs,
                             x => x.BookId,
                             y => y.BookId,
                             (x, y) => new {Recent = x, Favorite = y, x.Book, x.Book.Authors});

var recent = Repository.NewReads.Include(x => x.Book.Authors)
                       .Where(x => x.UserId == usersId);

var recent = Repository.NewReads.Include("Book").Where(n => n.UserId == usersId).FirstOrDefault().Book.Select(b=>b.Authors);