My son can read simple three- and four-letter words and I have found his progression has been much easier when one letter only is changing. I'm sure this is not news to anyone involved in education but I really don't know much about teaching small children! So for example cat, can, cap, and so on. So far I've just taught him by writing words out for him but I'm wondering is there a book along these lines we could use? He's got lots of books, lots of "my first word" books, and so on, but we don't have anything that is specifically about teaching reading.
Any help appreciated. He's 3.5.