When my DS was 3 and reading and it was not easy to find easy books like the bob books I created stories myself in word.
He loved Thomas the train so I put a picture in word and then just wrote simple sentences for him to read. Since it was about Thomas he was intererested. Don't know if that helps any.

My 2nd son is 3 now and man I can't get him to learn the letter A what a difference LOL