Creating new HaBtM?

Ok, I must be lame. Can't figure out how to create a new entry in my
HABTM models. I just want to add a new book with two authors.. How do
I do it?

class Author < ActiveRecord::Base
  has_and_belongs_to_many :books

class Books < ActiveRecord::Base
  has_and_belongs_to_many :authors

Your Books model should be called Book.
Once that's ok it's as easy as book.authors = [author_1, author_2]