DD could read a long list of words (her favorite things and names of favorite people, which she asked me to write out for her) somewhere when she was one (she could read the words in any context/order), but I say she really read at two when she could read a whole little book (probably a combo of sight words and phonics; we always said letter sounds rather than names and would help her figure out words with a quick note about like sh or silent k etc). When I was curious about if she was reading or memorizing I'd just find a new book (like a different Suess or Gerald and Piggy book) and listen in (but these early readers can switch to silent reading really fast so keep that in mind! She fooled her kindy teacher at first because of that).