var Id=1; 
var books = (from b in db.Books
                              where b.bookId == Id
                              select new
                              {
                                 //...

                              }).ToList();

var booksId= new list<int>(){ 1 , 2 , 6 , 7}; 
var books = (from b in db.Books
                              where b.bookId == ???
                              select new
                              {
                                 //...

                              }).ToList();