If I remember correctly son started reading at the end of Kindy, very rudamentary stuff. He was on to 'Magic Tree House' mid 1st grade, and 'Harry Potter' that summer.
He did have 'behavioral optometrist' type problems - not really problems, just slow-normal development and above average demands.
I've heard that short words are harder for kids with these visiual immaturities and difficulties and I'll bet contenxt helps too. Boring books have very little context.
DS12 was just 'regretting' that when I tried to teach him to read, I didn't take an 'ear-based' approach. He thinks that while he was in the car seat, I should have said: 'What do you get when you add 'B to A' and clapped if he said 'Ba' etc. Hindsight is always 20/20.
