Which techniques get a lesson?

Only the ones the book's puzzles need, beyond the simplest singles, in order from the simplest, up to 12 lessons per book. A book from Easy to Medium gets a few lessons; a book up to Evil gets up to 12. There are 25 lessons in all, including the killer techniques (cage combinations, the 45 rule, a cage locking a digit), thermometer order and arrow sums.