I know nothing about the AAR readers so if this isn’t helpful… oops. 😉 When my little ones have reached the silent e and th, sh, ch words, in addition to the reading lesson we’ll read maybe a paragraph from early books like Little Bear, Frog and Toad, and the Billy and Blaze series. I have my child read words they either know already or can figure out, and I read the more difficult ones.
Another good book is A Primary Reader by E. Louise Smythe. It’s on archive.org and is a collection of classic stories simplified for new readers. 🙂 This is a collection of similar books, retelling of Chaucer, Dante, the Odyssey, and others: https://issuu.com/librariesofhope3/stacks/2a2e98b4408440e29f1b103819971fbc You’ll likely need to do shared reading where you read some of the words for him.
Reading should be fun so he’ll love it for life. Don’t trudge!