My kid learned to read very early, likely as a side product of teaching her sign language where all the videos and cards also had the words.
She did not say a single word till she was 2. Never babbled either...but then I was the same as a kid. (early walker, late talker)
We also had those foam letters in the bathtub where I spelled simple words and sounded out the letters for her.
I sent her to a local pre-school when she was 2.5yrs, still only having about 5 words so I gave them this whole big list of signs so they could understand her.
Well, at pickup on the second day of school I was talking to the teacher when I heard a little voice in the corner saying "Red" "Yellow" Blue".
It was my girl, by herself, pointing at the words on the wall and reading them (by sight I imagine).
She still wasn't really 'reading' at 3, but loved to be read to. When nearly 4 and on the way to a doctor's appt, she says from the back seat "stop when red lights are flashing" . What red lights sweety? Where are the red lights?
Then I noticed the sign on the school bus in front of us "STOP when RED lights are flashing". She had read the entire thing. The little bugger kept all her talents secret!!