I have a three year old son, and we have a TON of alphabet books. It is awesome because he learned the alphabet through his favorite authors and characters: Eric Carle, Disney's Cars, and most recently Star Wars.
Many students on the spectrum need more structure and engagement when learning from books. This activity is perfect to help teach students on the spectrum in an interactive way. Just laminate the attached letters, add a flap to the back of the book, and you're good to go! Or, if you don't have access to a laminator, just use post it notes.
Here is list of some of my favorite alphabet books, all for less than $10 on Amazon!